Effects of near wall modeling in the Improved-Delayed-Detached-Eddy-Simulation (IDDES) methodology

The present study aims to assess the effects of two different underlying RANS models on overall behavior of the IDDES methodology when applied to different flow configurations ranging from fully attached (plane channel flow) to separated flows (periodic hill flow). This includes investigating prediction accuracy of first and second order statistics, response to grid refinement, grey area dynamics and triggering mechanism. Further, several criteria have been investigated to assess reliability and quality of the methodology when operating in scale resolving mode. It turns out that irrespective of the near wall modeling strategy, the IDDES methodology does not satisfy all criteria required to make this methodology reliable when applied to various flow configurations at different Reynolds numbers with different grid resolutions. Further, it is found that using more advanced underlying RANS model to improve prediction accuracy of the near wall dynamics results in extension of the grey area, which may delay the transition to scale resolving mode. This systematic study for attached and separated flows suggests that the shortcomings of IDDES methodology mostly lie in inaccurate prediction of the dynamics inside the grey area and demands further investigation in this direction to make this methodology capable of dealing with different flow situations reliably

Detection of Anomalies in the Quality of Electricity Supply

From the last two decades, power quality is getting much attention. Proper functioning of the equipment depends upon the quality of power supplied. Every year, demand of electric power goes on increasing and the power system network is expanding and becoming more complex. On account of thrust on clean power supply, use of renewable sources has dramatically increased in grid but it simultaneously causes power quality problems. In this work, power quality disturbance detection in wind farm integrated with grid is presented. For disturbance detection, time-time transform has been employed. The disturbance signal for the detection purpose is generated in MATLAB/Simulink environment by using a Simulink model

Development of an advanced Hybrid (U)RANS/LES turbulence models using Scale Adaptive Simulation (SAS) method

Title from PDF of title page, viewed August 24, 2022Dissertation advisors: Amirfarhang Mehdizadeh and Majid Bani-YaghoubVitaIncludes bibliographical references (pages 150-162)Dissertation (Ph.D)--Department of Civil & Mechanical Engineering, Department of Mathematics and Statistics. University of Missouri--Kansas City, 2022Turbulence is a ubiquitous phenomenon occurring in most practical fluid flows. The accurate prediction of turbulent flows is evident in optimizing and developing highly efficient modern fluid systems. Several turbulence models are available to investigate practical flows numerically and are broadly described among Reynolds-Averaged Navier- Stokes (RANS) and Large Eddy Simulation (LES) models. The RANS models are de- vised to model all the length scales of the associated flow field and provides often inaccu- rate results in complex flows such as flow separation and reattachment. In contrast, LES is primarily formulated to directly resolve the large scales and model the effect of the smaller scales. However, the mesh constraints become stringent in the near-wall region resulting in an exorbitant cost of LES methodology. In such cases, hybrid (U)RANS-LES models play a vital role as they perform as RANS in the near-wall region and LES in the regions away from the wall. However, currently available hybrid (U)RANS-LES model such as Improved Delayed Detached Eddy Simulation (IDDES) does not provide consis- tent performance under different fluid flow cases and suffers from several issues such as log-layer mismatch in attached flows, sensitivity to anisotropic grid design, and need for an ad-hoc turbulence generation mechanism for separated flows. Hence, this dissertation comprehensively assesses the IDDES methodology in dif- ferent flow cases. The response of grid designs/resolutions and different Reynolds num- bers are investigated. This study helps determine critical criteria to assess the ideal hybrid (U)RANS-LES model performance. Further, this investigation enables a deeper under- standing of various shortcomings encountered in the IDDES methodology and delivers better comprehension of the ideal hybrid (U)RANS-LES model. Finally, to overcome the shortcoming of the IDDES methodology, an advanced hybrid (U)RANS-LES model is devised. This dissertation introduces a modified hybrid (U)RANS-LES model, sensitized to non-equilibrium flow conditions such as flow separation. The numerical experiment of Decay of Homogeneous Isotropic Turbulence (DHIT) provides proof of accurately pre- dicting the non-equilibrium effects and returning to equilibrium at a high Reynolds num- ber. Further, the model is tested on the attached flows (turbulent channel flow) and sepa- rated flows (periodic hill and hump flow). Next, a new length scale equation (L-equation) is devised to mitigate the issue of log-layer mismatch (LLM) in attached flows, which provides an accurate description of the gray region (region which is neither (U)RANS nor LES). Further, a new automatic triggering mechanism is formulated utilizing the dy- namic behavior of the L-equation, and in conjunction with an advanced (U)RANS model (k − ε − ζ − f ), provides an accurate prediction of the turbulent channel flows. Additionally, the modified hybrid (U)RANS-LES model provides accurate pre- dictions on the highly anisotropic grid designs. In the case of separated flows, the mod- ified model accurately captures the separation and reattachment locations and provides a consistent response to different grid designs/resolutions. Moreover, for hump flow, the IDDES model requires ad-hoc turbulence fluctuations to sustain turbulence resolving ca- pabilities. The modified hybrid (U)RANS-LES model develops turbulent fluctuations arising from underlying flow instabilities after the flow separation and accurately predicts first and second-order flow quantities.Introduction -- Effects of near wall modeling in the improved-delayed-detached-eddy-simulation (IDDES) methodology -- Towards understanding and improving the transition between unsteady Reynolds-Averaged Navier-Stokes (URANS) and large eddy simulation (LES) in hybrid URANS-LES methodology -- Conclusion and outline of the dissertatio

Review of Detection and Classifcation Techniques for Power Quality Events

This paper presents a short review on the field of power quality. Power quality is directly related to the performance of the electric equipment. The accurate and reliable operation and life of equipment based on the quality of input power. So the main concern on the power quality is for satisfactory operation of each connected equipment. Detection, classification and mitigation are the main steps used in the power quality analysis. Accurate detection and classification gives effective mitigation solutions. A number of research papers are reviewed and presented here which gives some knowledge about power quality field

A Review on Speech Recognition Methods

Voice recognition is the identification of a speaker on the basis of the characteristics of voices. For this, features of speech patterns that differ between individuals are used to achieve the objective. In this paper speaker recognition system are discussed. Implementation of speaker's voice recognition system with MATLAB makes possible use of voice for real life applications. This paper provides a brief review of different DSP based techniques applied for speech recognition

Brucellosis - A major differential for juvenile idiopathic arthritis

Brucellosis is a Gram-negative, aerobic zoonotic infection acquired by Brucella species and transmitted from animals to humansthrough the ingestion of infected food products, direct contact with an infected animal, or inhalation of aerosols. Usually, thedisease remains undiagnosed due to lack of awareness and inadequate reporting and is a challenging health problem in tropicalcountries. We report a case of 16-year-old male presenting to us with chronic inflammatory symmetric polyarthritis misdiagnosedas juvenile idiopathic arthritis but later found to be suffering from brucellosis on reevaluation. Through this case report, we wouldlike to highlight the possibility and advantage of the high degree of suspicion for an infectious etiology responsible for arthritis inthe background of autoimmunity and would also like to emphasize on the possibility of Brucella inducing a false-positive responsefor young patients presenting with arthritis

Identifying suicide and self-harm research priorities in North West England: a Delphi study

Background: Understanding and effectively managing self-harm and suicide requires collaborative research between stakeholders focused on shared priorities. Aims: To develop a consensus about suicide and self-harm research priorities in the North-West of England using the Delphi method. Method: Items for the Delphi survey were generated through group discussions at a workshop with 88 stakeholders and subsequent thematic analysis of key themes. Forty-four participants who were experts-by-experience, researchers, and clinicians based within health services including third sector organisations completed the Delphi survey. Results: A three-round survey reached consensus on 55 research priority items identifying key priorities in each of the following groups: offenders, children and young people, self-harm in community settings, and crisis care in the community. Limitation: The pool of delegates at the workshop and subsequent self-selection into the Delphi may have introduced bias into the study. Conclusion: The current paper highlights specific actionable priorities were identified in four areas that can be used to inform research efforts and future policy and practice, based on shared areas of perceived importance and concern. Future work is needed to confirm the significance of these priority areas, including the use of evidence synthesis approaches to ascertain the extent to which these priorities have already been investigated and where gaps in understanding remain

Effects of Near Wall Modeling in the Improved-Delayed-Detached-Eddy-Simulation (IDDES) Methodology

The present study aims to assess the effects of two different underlying RANS models on overall behavior of the IDDES methodology when applied to different flow configurations ranging from fully attached (plane channel flow) to separated flows (periodic hill flow). This includes investigating prediction accuracy of first and second order statistics, response to grid refinement, grey area dynamics and triggering mechanism. Further, several criteria have been investigated to assess reliability and quality of the methodology when operating in scale resolving mode. It turns out that irrespective of the near wall modeling strategy, the IDDES methodology does not satisfy all criteria required to make this methodology reliable when applied to various flow configurations at different Reynolds numbers with different grid resolutions. Further, it is found that using more advanced underlying RANS model to improve prediction accuracy of the near wall dynamics results in extension of the grey area, which may delay the transition to scale resolving mode. This systematic study for attached and separated flows suggests that the shortcomings of IDDES methodology mostly lie in inaccurate prediction of the dynamics inside the grey area and demands further investigation in this direction to make this methodology capable of dealing with different flow situations reliably

Tracing geochemical sources and health risk assessment of uranium in groundwater of arid zone of India

Water quality degradation and metal contamination in groundwater are serious concerns in an arid region with scanty water resources. This study aimed at evaluating the source of uranium (U) and potential health risk assessment in groundwater of the arid region of western Rajasthan and northern Gujarat. The probable source of vanadium (V) and fluorine (F) was also identified. U and trace metal concentration, along with physicochemical characteristics were determined for 265 groundwater samples collected from groundwater of duricrusts and palaeochannels of western Rajasthan and northern Gujarat. The U concentration ranged between 0.6 and 260 μg L−1 with a mean value of 24 μg L−1, and 30% of samples surpassed the World Health Organization’s limit for U (30 μg L−1). Speciation results suggested that dissolution of primary U mineral, carnotite [ K2(UO2)2(VO4)2·3H2O] governs the enrichment. Water–rock interaction and evaporation are found the major hydrogeochemical processes controlling U mineralization. Groundwater zones having high U concentrations are characterized by Na–Cl hydrogeochemical facies and high total dissolved solids. It is inferred from geochemical modelling and principal component analysis that silicate weathering, bicarbonate complexation, carnotite dissolution, and ion exchange are principal factors controlling major solute ion chemistry. The annual ingestion doses of U for all the age groups are found to be safe and below the permissible limit in all samples. The health risk assessment with trace elements manifested high carcinogenic risks for children