Mathematical Modelling of Energy Systems and Fluid Machinery

The ongoing digitalization of the energy sector, which will make a large amount of data available, should not be viewed as a passive ICT application for energy technology or a threat to thermodynamics and fluid dynamics, in the light of the competition triggered by data mining and machine learning techniques. These new technologies must be posed on solid bases for the representation of energy systems and fluid machinery. Therefore, mathematical modelling is still relevant and its importance cannot be underestimated. The aim of this Special Issue was to collect contributions about mathematical modelling of energy systems and fluid machinery in order to build and consolidate the base of this knowledge

Investigation of the Performance of a Centrifugal Pump Impeller Design with the Addition of a Junction Disc Plate

This research analyzes the impeller design performance that has been modified based on previous impeller designs. The previous impeller design used high engine power consumption due to the total head, so the modification of the impeller design is expected to reduce the engine power consumption. The existing design and the modified impeller design with the addition of the junction disc plate are used by this research. This research used experiment methods and theoretical methods to compare both of impeller design performances. The experiment method measures total head, fluid capacity, engine speed, and engine power consumption. The theoretical method analyzes actual fluid velocity, specific velocity, total suction head, NPSH, and pump efficiency. The results showed that the fluid flow rate was able to increase the efficiency of the centrifugal pump by 2.8%. The conclusion explains that the addition of a junction disc plate produces energy from a steady fluid flow rate to reduce the engine power consumption and escalation of pump efficiency

Identification of Water Hammering for Centrifugal Pump Drive Systems

Water hammering is a significant problem in pumping systems. It damages the pipelines of the pump drastically and needs to identify with an intelligent method. Various conventional methods such as the method of characteristics and wave attenuation methods are available to identify water hammering problems, and the predictive control method is one of the finest and time-saving methods that can identify the anomalies in the system at an early stage such that the device can be saved from total damage and reduce energy loss. In this research, a machine learning (ML) algorithm has used for a predictive control method for the identification of water hammering problems in a pumping system with the help of simulations and experimental-based works. A linear regression algorithm has been used in this work to predict water hammering problems. The efficiency of the algorithm is almost 90% compared to other ML algorithms. Through a Vib Sensor app-based device at different pressures and flow rates, the velocity of the pumping system, a fluctuation between healthy and faulty conditions, and acceleration value at different times have been collected for experimental analysis. A fault created to analyze a water hammering problem in a pumping system by the sudden closing and opening of the valve. When the valve suddenly closed, the kinetic energy in the system changed to elastic resilience, which created a series of positive and negative wave vibrations in the pipe. The present work concentrates on the water hammering problem of centrifugal pumping AC drive systems. The problem is mainly a pressure surge that occurs in the fluid, due to sudden or forced stops of valves or changes in the direction and momentum of the fluid. Various experimental results based on ML tool and fast Fourier transformation (FFT) analysis are obtained with a Vib Sensor testbed set-up to prove that linear regression analysis is the less time-consuming algorithm for fault detection, irrespective of data size

Rumo a uma metodologia de manutenção preditiva de bombas hidráulicas

Hydraulic pumps, essential elements in water supply systems, are mainly responsible for the high energy consumption associated with these systems. It is, therefore, relevant to keep the pumps running in their best possible conditions in order to avoid further consumption and costs, and also to anticipate possible pump failures. The best strategy to anticipate the occurrence of failures is to implement preventive and predictive maintenance plans, instead of corrective maintenance that is still widely applied. Thus, with the goal of developing a predictive maintenance methodology applied to hydraulic pumps, this dissertation aims to explore and investigate the applicability of two techniques that can be integrated into a maintenance plan: the detection and classification of failures and the estimation of the remaining useful life (RUL) of the pump. To implement the proposed tasks, simulated data and measured data from real systems were used, taken from online data repositories, with values recorded by sensors and with the identified condition of the system. The first technique allowed, through sensor data with the respectively identified faults, to train classification algorithms able to identify failures. In the first of the evaluated case studies, the best of the implemented algorithms identified the failures associated with the pump data with an accuracy of 82.9%, whereas, in the second of the evaluated case studies, the algorithm that presented the best performance obtained an accuracy of 94.6% in identifying the failure mode associated with the pump. The decision tree and ensemble trees algorithms proved to be the most suitable for the studied purpose. The second technique allowed to estimate RUL values from sensor data recorded from normal operation to system failure. Although the first RUL implemented case study was an engine, the second case study was a water pump. The methodology of the RUL model proved to be relevant because it managed, even with some deviations from the true values, to estimate acceptable values of RUL. An economic analysis was also carried out, highlighting the relevance of applying RUL estimation models in predictive maintenance methodologies for hydraulic pumpsAs bombas hidráulicas, elementos essenciais nos sistemas de abastecimento de água, são os principais responsáveis pelos elevados consumos energéticos associados a estes sistemas. Torna-se, portanto, relevante manter as bombas a funcionar nas suas melhores condições possíveis de forma a evitar mais consumos e custos, e também antecipar possíveis falhas nas bombas. A melhor estratégia para antecipar o acontecimento de falhas passa pela implementação de planos de manutenção preventivos e preditivos, ao invés da manutenção corretiva que é ainda muito aplicada. Assim, com vista ao desenvolvimento de uma metodologia de manutenção preditiva aplicada às bombas hidráulicas, esta dissertação tem como objetivo a exploração e investigação da aplicabilidade de duas técnicas que podem ser integradas num plano de manutenção: a deteção e classificação de falhas e a estimativa do tempo de vida útil restante (RUL) de uma bomba. Para implementar as tarefas propostas utilizaram-se dados simulados e dados medidos a partir de sistemas reais, retirados de repositórios de dados online, com valores registados por sensores e com a condição do sistema identificada. A primeira técnica permitiu, através de dados de sensores com as respetivas falhas identificadas, treinar algoritmos de classificação capazes de identificar falhas. No primeiro dos casos de estudo avaliados, o melhor dos algoritmos implementados identificou as falhas associadas aos dados da bomba com uma classificação de desempenho de 82.9%, ao passo que, no segundo dos casos de estudo avaliados, o algoritmo que apresentou melhor desempenho obteve uma classificação de 94.6% na identificação do modo de falha associado à bomba. Os algoritmos de decision trees e ensemble trees demonstraram ser os mais indicados para o propósito estudado. A segunda técnica permitiu calcular previsões de valores do RUL a partir de dados de sensores registados desde uma operação normal até à falha do sistema. Apesar de o primeiro caso de estudo de implementação de RUL ter sido um motor, o segundo caso de estudo foi uma bomba de água. A metodologia do modelo de RUL demonstrou ser pertinente pois conseguiu, ainda que com alguns desvios em relação aos verdadeiros valores, estimar valores aceitáveis de RUL. Elaborou-se ainda uma análise económica que evidencia a relevância em aplicar modelos de cálculo de RUL em metodologias de manutenção preditiva de bombas hidráulicasMestrado em Engenharia Mecânic

Design and development of a pulsatile axial flow blood pump as a left ventricular assist device

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonEach year all over the world, Millions of patients from infants to adults are diagnosed with heart failure. A limited number of donor hearts available for these patients results in a tremendous demand of mechanical circulatory support (MCS) system, either in the form of total artificial heart (TAH) or a ventricular assist device (VAD). Physiologically MCS are expected to provide heart; a time to rest and potential recovery by unloading the ventricle, while maintaining the adequate peripheral as well as coronary circulation. Existing ventricular assist devices (VAD) have employed either displacement type pulsatile flow pumping systems or continuous flow type centrifugal/rotodynamic pumps systems. Displacement type devices produce a pulsatile outflow, which has significant benefits on vital organ function and end organ recovery. Continuous flow devices are small and can be placed within body using minimal invasive procedures, in addition they reduces infection as well as mechanical failure related complications. Despite availability of success stories for both types of pumping systems, the selection of the either of them is an ongoing debate. This thesis aims to merge the advantages of displacement pumps (pulsatile flow) and axial-flow pumps (continuous flow) into a novel left vertical assist device (LVAD), by designing a novel minimal invasive, miniature axial-flow pump producing pulsating outflow for the patients having early heart failure and myocardial infarction as a Bridge-To-Recovery (BTR) or Bridge-To-Decision (BTD) device. The design of VAD, the experimental setup and dedicated control system were developed for the in vitro evaluation of pulsatile flow. Computational fluid dynamics (CFD) had been employed for the detail investigation of pulsatile flow. In addition, CFD was also applied to optimize the pulse generation for low haemolysis levels. Outcome of the study produces comprehensive understanding for the generation of pulsatile flow using an axial flow pump. Further, it provides the means of generating a controlled pulse that can regulate flow rate for varying heart rate within low haemolysis levels

Towards patient-specific modelling as a pre-operative planning strategy and follow up assessment for the treatment of advanced heart failure with rotary blood pumps

Background: Ventricular Assist Devices (VADs) insertion is an established treatment for patients with end-stage heart failure waiting for a heart transplant or in need for long-term circulatory support (destination therapy). Rotary blood pumps (RBP) are the most popular devices in view of their size and performance. Pre-operative planning strategy for the insertion of a left ventricular assist device (LVAD) requires a timely discussion at a Multi-Disciplinary Team Meeting (MDT). Clinical-decision making is based according to the needs of the patient and must be processed without delays. Nevertheless, thrombus formation remains a feared complication which affects outcome. VADs operate in a flow regime which is difficult to simulate: the transitional region at the boundary of laminar and turbulent flow (low Reynolds number). Different methods have been used but the best approach remains debatable. Computational Fluid Dynamics (CFD) is an attractive and invaluable tool for the study of the interactions between VADs and the cardiovascular system. The aim of this thesis is three-fold: a) to investigate the use of pressure-volume analysis in a clinical setting through the review of six heart failure patients previously discussed at a MDT meeting with a view to predict or guide further management; b) to review the theory behind modelling approaches to VADs and their interactions with the cardiovascular system for better understanding of their clinical use. Then, an overview of computational fluid dynamics (CFD) is considered as a prelude to its application to the analysis of VADs performance. Additionally, the development of a simplified model of centrifugal pump will be used in initial simulations as preliminary analysis; c) to examine an example of a proof-of-concept pilot patient-specific model of an axial flow pump (HeartMate II) as pre-operative planning strategy in a patient-specific model with a view to identify potential critical areas that may affect pump function and outcome in a clinical setting. Material and Methods: 3D reconstruction from CT-scan images of patients who underwent the insertion of rotary blood pumps, namely HeartWare HVAD and HeartMate II. Ansys Fluent has been used for CFD analysis based on the fundamental governing equations of motion. Blood has been modelled as incompressible, Newtonian fluid with density = 1060 and viscosity = 0.0035 kg/m-s. The laminar and SST models have been used for comparison purposes. The rotational motion of the impeller has been implemented using the moving reference frame (MRF) approach. The sliding mesh method has also been used to account for unsteady interaction between stationary and moving part. The no-slip condition has been applied to all walls, which were assumed to be rigid. Boundary conditions consisting of velocity inlet and pressure outlet of the pump based on different settings and constant rotational speed for the impeller. Pressure-velocity coupling has been based on the coupled scheme. Spatial discretisation consisted of the “least square cell based” gradient for velocity and “PRESTO” or second order for pressure. Second order upwind has been set for the momentum, turbulent kinetic energy and specific dissipation rate. First order implicit has been set for transient formulation. The pseudo transient algorithm (steady state), the high order relaxation term and the warped-face gradient correction have been used to add an unsteady term to the solution equations with the aim to improve stability and enhance convergence. Specific settings have been considered for comparison purposes. Results: Pressure-volume simulation analysis in six advanced heart failure patients showed that an integrated model of the cardiovascular system based on lumped-parameter representation, modified time-varying elastance and pressure-volume analysis of ventricular function seems a feasible and suitable approach yielding a sufficiently accurate quantitative analysis in real time, therefore applicable within the time-constraints of a clinical setting. Lumped-parameter models consist of simultaneous ordinary differential equations complemented by an algebraic balance equation and are suitable for examination of global distribution of pressure, flow and volume over a range of physiological conditions with inclusion of the interaction between modelled components. Higher level lumped-parameter modelling is needed to address the interaction between the circulation and other systems based on a compromise between complexity and ability to set the required parameters to personalise an integrated lumped-parameter model for a patient-specific approach. CARDIOSIM© fulfils these requirements and does address the systems interaction with its modular approach and assembly of models with varying degree of complexity although 0-D and 1-D coupling may be required for the evaluation of long-term VAD support. The challenge remains the ability to predict outcome over a longer period of time. The preliminary CFD simulations with the HeartWare HVAD centrifugal pump demonstrated that it is possible to obtain an accurate analysis in a timely manner to complement the clinical review process. The simulations with the pilot patient-specific model of the HeartMate II axial flow pump revealed that a complex 3D reconstruction is feasible in a timely manner and can be used to generate sufficiently accurate results to be used in the context of a MDT meeting for the purposes of clinical decision-making. Overall, these three studies demonstrate that the time frame of the simulations was within hours which may fit the time constraints of the clinical environment in the context of a MDT meeting. More specifically, it was shown that the laminar model may be used for an initial evaluation of the flow development within the pump. Nonetheless, the k- model offers higher accuracy if the timeline of the clinical setting allows for a longer simulation. Conclusion: This thesis aimed at the understanding of the use of computational modelling as a pre-operative planning strategy and follow up assessment for the treatment of advanced heart failure with rotary blood pumps. The novelty lays in the use of both pressure-volume simulation analysis and 3D flow dynamics studies in VADs with a view to treatment optimisation and outcome prediction within the time constraints of a clinical setting in the context of a MDT meeting. The clinical significance and the contribution to the field is a more targeted approach for different groups of patients and a more quantitative evaluation in the clinical decision process based on a pro-active co-operation between clinicians and scientists reducing the potential for “guess work”. The results of this thesis are a proof-of-concept as a prelude to a potential future implementation of patient-specific modelling within a clinical setting on a daily basis demonstrating a clear clinical significance and contribution to the field. The proposed approach does not consider modelling and simulation as a substitute for clinical experience but an additional tool to guide therapeutic intervention and complement the clinical decision process in which the clinician remains the ultimate decision-maker. Such an approach may well add a different dimension to the problem of heart failure with potential for high return in terms of patient’s outcome and long-term surveillance. The same principles would be applicable to other cardiovascular problems in line with the current concept of “Team Approach” such as the Heart Team, the Structural Heart Team or the Aortic Team. The present work has taken this concept closer to clinical delivery and has highlighted its potential but further work remains to be done in refining the technique.Background: Ventricular Assist Devices (VADs) insertion is an established treatment for patients with end-stage heart failure waiting for a heart transplant or in need for long-term circulatory support (destination therapy). Rotary blood pumps (RBP) are the most popular devices in view of their size and performance. Pre-operative planning strategy for the insertion of a left ventricular assist device (LVAD) requires a timely discussion at a Multi-Disciplinary Team Meeting (MDT). Clinical-decision making is based according to the needs of the patient and must be processed without delays. Nevertheless, thrombus formation remains a feared complication which affects outcome. VADs operate in a flow regime which is difficult to simulate: the transitional region at the boundary of laminar and turbulent flow (low Reynolds number). Different methods have been used but the best approach remains debatable. Computational Fluid Dynamics (CFD) is an attractive and invaluable tool for the study of the interactions between VADs and the cardiovascular system. The aim of this thesis is three-fold: a) to investigate the use of pressure-volume analysis in a clinical setting through the review of six heart failure patients previously discussed at a MDT meeting with a view to predict or guide further management; b) to review the theory behind modelling approaches to VADs and their interactions with the cardiovascular system for better understanding of their clinical use. Then, an overview of computational fluid dynamics (CFD) is considered as a prelude to its application to the analysis of VADs performance. Additionally, the development of a simplified model of centrifugal pump will be used in initial simulations as preliminary analysis; c) to examine an example of a proof-of-concept pilot patient-specific model of an axial flow pump (HeartMate II) as pre-operative planning strategy in a patient-specific model with a view to identify potential critical areas that may affect pump function and outcome in a clinical setting. Material and Methods: 3D reconstruction from CT-scan images of patients who underwent the insertion of rotary blood pumps, namely HeartWare HVAD and HeartMate II. Ansys Fluent has been used for CFD analysis based on the fundamental governing equations of motion. Blood has been modelled as incompressible, Newtonian fluid with density = 1060 and viscosity = 0.0035 kg/m-s. The laminar and SST models have been used for comparison purposes. The rotational motion of the impeller has been implemented using the moving reference frame (MRF) approach. The sliding mesh method has also been used to account for unsteady interaction between stationary and moving part. The no-slip condition has been applied to all walls, which were assumed to be rigid. Boundary conditions consisting of velocity inlet and pressure outlet of the pump based on different settings and constant rotational speed for the impeller. Pressure-velocity coupling has been based on the coupled scheme. Spatial discretisation consisted of the “least square cell based” gradient for velocity and “PRESTO” or second order for pressure. Second order upwind has been set for the momentum, turbulent kinetic energy and specific dissipation rate. First order implicit has been set for transient formulation. The pseudo transient algorithm (steady state), the high order relaxation term and the warped-face gradient correction have been used to add an unsteady term to the solution equations with the aim to improve stability and enhance convergence. Specific settings have been considered for comparison purposes. Results: Pressure-volume simulation analysis in six advanced heart failure patients showed that an integrated model of the cardiovascular system based on lumped-parameter representation, modified time-varying elastance and pressure-volume analysis of ventricular function seems a feasible and suitable approach yielding a sufficiently accurate quantitative analysis in real time, therefore applicable within the time-constraints of a clinical setting. Lumped-parameter models consist of simultaneous ordinary differential equations complemented by an algebraic balance equation and are suitable for examination of global distribution of pressure, flow and volume over a range of physiological conditions with inclusion of the interaction between modelled components. Higher level lumped-parameter modelling is needed to address the interaction between the circulation and other systems based on a compromise between complexity and ability to set the required parameters to personalise an integrated lumped-parameter model for a patient-specific approach. CARDIOSIM© fulfils these requirements and does address the systems interaction with its modular approach and assembly of models with varying degree of complexity although 0-D and 1-D coupling may be required for the evaluation of long-term VAD support. The challenge remains the ability to predict outcome over a longer period of time. The preliminary CFD simulations with the HeartWare HVAD centrifugal pump demonstrated that it is possible to obtain an accurate analysis in a timely manner to complement the clinical review process. The simulations with the pilot patient-specific model of the HeartMate II axial flow pump revealed that a complex 3D reconstruction is feasible in a timely manner and can be used to generate sufficiently accurate results to be used in the context of a MDT meeting for the purposes of clinical decision-making. Overall, these three studies demonstrate that the time frame of the simulations was within hours which may fit the time constraints of the clinical environment in the context of a MDT meeting. More specifically, it was shown that the laminar model may be used for an initial evaluation of the flow development within the pump. Nonetheless, the k- model offers higher accuracy if the timeline of the clinical setting allows for a longer simulation. Conclusion: This thesis aimed at the understanding of the use of computational modelling as a pre-operative planning strategy and follow up assessment for the treatment of advanced heart failure with rotary blood pumps. The novelty lays in the use of both pressure-volume simulation analysis and 3D flow dynamics studies in VADs with a view to treatment optimisation and outcome prediction within the time constraints of a clinical setting in the context of a MDT meeting. The clinical significance and the contribution to the field is a more targeted approach for different groups of patients and a more quantitative evaluation in the clinical decision process based on a pro-active co-operation between clinicians and scientists reducing the potential for “guess work”. The results of this thesis are a proof-of-concept as a prelude to a potential future implementation of patient-specific modelling within a clinical setting on a daily basis demonstrating a clear clinical significance and contribution to the field. The proposed approach does not consider modelling and simulation as a substitute for clinical experience but an additional tool to guide therapeutic intervention and complement the clinical decision process in which the clinician remains the ultimate decision-maker. Such an approach may well add a different dimension to the problem of heart failure with potential for high return in terms of patient’s outcome and long-term surveillance. The same principles would be applicable to other cardiovascular problems in line with the current concept of “Team Approach” such as the Heart Team, the Structural Heart Team or the Aortic Team. The present work has taken this concept closer to clinical delivery and has highlighted its potential but further work remains to be done in refining the technique

Design, Fabrication and Performance of Wind Turbines 2020

From small-scale vertical axis wind turbines for urban usage to large-scale horizontal axis wind turbines for offshore wind farms, design, fabrication, and optimization technologies are highly required to manage wind energy effectively. Moreover, some new opportunities, such as in wind farm design, fluid–structure interaction, aero-acoustics, fabrication methods and performance tests by experimental and computational fluid dynamics should be engaged in modern wind turbine communities. The basic objectives of this book include improving the reliability and promoting the high efficiency of wind turbines as well as their dynamic performance, reducing wind turbine-generated noise and improving power generation efficiencies through high-fidelity approaches. Students, scholars, and engineers who manage such a wide range of wind turbine scales and usages, design, fabrication, and performance test protocols for various wind turbines, are highly recommended to read this book

Evaluation of CFD based hemolysis prediction methods

Accurate quantitative evaluation of shear stress-related hemolysis (destruction of red blood cells) could be used to improve blood handling devices, including left ventricular assist devices (LVAD). Computational Fluid Dynamics (CFD) predicts the fluid dynamics of complex pump geometry and has been used to track the shear stress history of red blood cells as they travel through these devices. Several models that predict the relationship between hemolysis, shear stress and exposure time have been used to evaluate the hemolysis in the pumps. However, the prediction accuracy has not reached the satisfactory level. The goal of my thesis is to investigate the application of CFD in determining hemolysis using different hemolysis prediction methods. • This approach is two-fold. First it is done on a simplified geometry designed to produce known and controllable shear stresses. This device is known as the mag-lev shearing device and was designed using CFD in order to study erythrocyte damage in terms of the effects of shear stress. This mathematical solution for annular shearing device will be used to verify computational data. • Secondly, I applied the same methods to the LEV-VAD pump, currently under development at RIT. The grid independent mesh was obtained for RIT axial pump and was utilized for further studies. In Characteristic curve (Pressure vs. Flow), the experimental pressure rise data was compared with the pressure difference data from CFD simulation of the RIT mini pump. • Hemolysis was estimated for both geometries using four different hemolysis analysis methods, referred to as: Threshold Value, Mass-Weighted Average, Eulerian and Lagrangian approaches. The pump numerical hemolysis predictions are compared with the previous in vitro hemolysis data using bovine blood. The numerical simulation of flow field for mag-lev shearing device was compared with the analytical solution of the fluid dynamics inside the gap regions of the device. In the future, the mag-lev shearing device will be used with animal and human blood to empirically evaluate the hemolysis and this empirical data may be used to validate the numerical methods presented here