Computational Fluid Dynamics as an Emerging Supporting Clinical Tool: Review on Human Airways

Objectives: The main objective of this review article is to evaluate the usability of Computational Fluid Dynamics (CFD) as a supporting clinical tool for respiratory system. Data Source: The English articles referred for this review paper were identified from various International peer reviewed journals indexed in Science citation index. Study Selection: 26 high quality articles most relevant to the highlighted topic which were published in last fifteen years were selected from almost 120 articles. Results: The analysis done and the outcome obtained by this computational method is as accurate as Spirometry and Pulmonary function test (PFT) result. CFD can be very useful in the cases where patents is unable to perform PFT. Pressure drop, Velocity profile, Wall shear stress & other flow parameter, respiratory resistance, Pattern of drug deposition, Particles transport/deposition, etc. had also been predicted accurately using CFD. The effect of tracheal stenosis on the flow parameters has been predicted. The size and location of tracheal stenosis has also been correlated with breathing difficulties. The distribution of air in various lobes of the lungs can be accurately predicted with CFD tool. Conclusion: Virtual surgery is eventually possible by using CFD after further research with validation. With the help of this multi - disciplinary and efficient tool we can obtain accurate result while reducing cost and time

Shell side numerical analysis of a shell and tube heat exchanger considering the effects of baffle inclination angle on fluid flow using CFD

In this present study, attempts were made to investigate the impacts of various baffle inclination angles on fluid flow and the heat transfer characteristics of a shell-and-tube heat exchanger for three different baffle inclination angles namely 0°,10° and 20°. The simulation results for various shell and tube heat exchangers, one with segmental baffles perpendicular to fluid flow and two with segmental baffles inclined to the direction of fluid flow are compared for their performance. The shell side design has been investigated numerically by modeling a small shell-and-tube heat exchanger. The study is concerned with a single shell and single side pass parallel flow heat exchanger. The flow and temperature fields inside the shell are studied using non-commercial CFD software tool ANSYS CFX 12.1. For a given baffle cut of 36 %, the heat exchanger performance is investigated by varying mass flow rate and baffle inclination angle. From the CFD simulation results, the shell side outlet temperature, pressure drop, recirculation near the baffles, optimal mass flow rate and the optimum baffle inclination angle for the given heat exchanger geometry are determined

Effect of pongamia biodiesel on emission and combustion characteristics of DI compression ignition engine

Biodiesel produced from pongamia oil has been considered as promising option for diesel engines because of its environmental friendliness. In this work, bio-diesel from pongamia oil is prepared (PME 100), tested on a diesel engine for different blends such as PME 20, PME 40, PME 60 and PME 80. Comparison is made with diesel operation. Parameters such as brake thermal efficiency, brake specific fuel consumption, carbon monoxide, unburned hydrocarbons, smoke and NOx emissions are evaluated. Even though the performance reduces slightly when the engine is fueled with biodiesel, significant changes in the combustion parameters observed in case of biodiesel blends are significant to note. On the other hand, reduction in CO, HC and smoke is observed. Study reveals the effect of bio-diesel on a DI engine when compared to diesel and evolves conclusions with respect to performance and emissions

Experimental study of recirculating flows induced by vane swirler

14-22The core objective of this study is to present the details of the experimental procedure and measurements made in an axisymmetric swirler model. The flow through 8 blade 30º vane swirler is studied experimentally. An overlap angle of 30º is provided between the vanes for the proper guidance of the flow through swirler. A hemi spherical bluff body is attached to the hub in order to overcome the inlet flow field distortion. A 5 mm diameter five-hole pitot sphere of cobra type has been used along with electronic digital manometers for the measurements. A computer aided traversing mechanism supported with Streamware software automatically controls the traversing of the probe. The recirculation velocities at the center core and corner regions are well captured with the five-hole probe. Five-hole pitot probe measurements along the entire length of the model at different stations, allow the determination of axial mean velocity component and pressure field parameters, which provide comprehensive information to aid and understand such complex recirculation flows. Flow field characteristics downstream of the swirler at different axial locations are examined in detail. The recirculation length and width are found to be strongly dependent on the amount of turbulence created by the vane swirler

Influence of aspect ratio on the thermal performance of rectangular shaped micro channel heat sink using CFD code

A numerical study has been carried out to investigate the heat transfer enhancement and fluid flow characteristics for various aspect ratios of rectangular micro channel heat sinks (MCHS). The working fluid considered for the analysis is water. The fluid flow and heat transfer characteristics of a three-dimensional MCHS are obtained numerically by solving the appropriate governing equations. The flow domain is discretized as finite volume elements and solved using ANSYS CFX 14.5, commercially available CFD code. The numerically predicted results obtained through CFD code are validated with the experiments carried out and it is found that the maximum deviation between the two is less than 5%. Hence the CFD code is further extended to study the influence of geometrical parameters. The channel size optimization has been carried out numerically to obtain the effective heat removal from the MCHS. Average convective heat transfer coefficient, outlet temperature, friction and pressure drop, pumping power and thermal resistance have been plotted against Reynolds number. Non-dimensional parameter, Nusselt number has been plotted as a function of Reynolds number for three heat sinks with different aspect ratios. Friction factor and pressure drop across the channels are obtained and plotted across the channels

NUMERICAL SIMULATION OF HEAT TRANSFER CHARACTERISTICS IN THE ABSORBER TUBE OF PARABOLIC TROUGH COLLECTOR WITH INTERNAL FLOW OBSTRUCTIONS

ABSTRACT Absorber tube performance enhancement by using passive techniques is one of the major topics of research in the field of solar thermal power engineering. Earlier studies on ducts revealed that passive augmentation techniques have shown considerable enhancement in heat transfer. Experiments were conducted earlier on Parabolic Trough Collector (PTC) with plain absorber tube without inserts for different flow rate conditions. It was observed that fluid flow rate with 85 kg/hr has shown higher temperature difference for solar flux condition of 850 W/m 2 . In the present study, numerical analysis using CFD is performed by using inserts of different cross-section inside the fluid flow path of an absorber tube to study the flow characteristics. The fluid flow and heat transfer phenomena through a 3-dimensional absorber tube with varying heat source are obtained by solving the fundamental governing equations namely: conservation of mass, momentum and energy. Turbulence is modeled using SST k-ω model of closure. The heat transfer and pressure drop is calculated from the studies conducted for a mass flow rate of 85 kg/hr using the ANSYS CFX 12.1 software. The result of the numerical analysis is validated with the experiments carried out with the parabolic trough collector. The numerical study is carried out with triangle, inverted triangle and semi-circular inserts and compared with that of plain absorber tube. It has been found that triangle insertion gives optimized results with respect to uniform heat transfer which reduces the thermal fatigue even the pressure drop is relatively high compared to the plain absorber tube without insertion

EXAMINATION OF THE LATTICE BOLTZMANN METHOD IN SIMULATION OF MANUFACTURING

ABSTRACT This work is concerned with the characteristics of incompressible viscous flow inside a two-sided lid-driven cavity with its two opposite walls moving with a constant velocity in parallel direction and in antiparallel direction by Lattice Boltzmann method (LBM). The model used in the present work is two-dimensional nine-velocity (D2Q9) square lattice as it gives more stable and accurate result when compared to two-dimensional seven-velocity (D2Q7) hexagonal lattice. The characteristics of flow problem are investigated for different Reynolds number and also for aspect ratio, K = 2.0 and 5.0. The formation of different vortices with the variation of Reynolds number for parallel and antiparallel motion is studied in detail. To sum up, the present study reveals many interesting features of two-sided lid-driven deep cavity flows and demonstrates the capability of the Lattice Boltzmann method to capture these features