Flow and Heat Transfer Analysis in a Single Row Narrow Impingement Channel: Comparison of PIV, LES, and RANS to Identify RANS Limitations

2017 ◽  
Author(s):  
Jahed Hossain ◽  
Erik Fernandez ◽  
Christian Garrett ◽  
Jay Kapat
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Field ◽  
Mean Flow ◽  
Single Row ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics ◽  
Flow Phenomena ◽  
The Mean ◽  
Channel Configuration

The present study aims to understand the flow, turbulence, and heat transfer in a single row narrow impingement channel for gas turbine heat transfer applications. Since the advent of several advanced manufacturing techniques, narrow wall cooling schemes have become more practical. In this study, the Reynolds number based on jet diameter was ≃15,000, with the jet plate having fixed jet hole diameters and hole spacing. The height of the channel is 3 times the impingement jet diameter. The channel width is 4 times the jet diameter of the impingement hole. The channel configuration was chosen such that the crossflow air is drawn out in the streamwise direction (maximum crossflow configuration). The impinging jets and the wall jets play a substantial role in removing heat in this kind of configuration. Hence, it is important to understand the evolution of flow and heat transfer in a channel of this configuration. The dynamics of flow and heat transfer in a single row narrow impingement channel are experimentally and numerically investigated. Particle Image Velocimetry (PIV) was used to reveal the detailed information of flow phenomena. The detailed PIV experiment was performed on this kind of impingement channel to satisfy the need for experimental data for this kind of impingement configuration, in order to validate turbulence models. PIV measurements were taken at a plane normal to the target wall along the jet centerline. The mean velocity field and turbulent statistics generated from the mean flow field were analyzed. The experimental data from the PIV reveals that flow is highly anisotropic in a narrow impingement channel. To support experimental data, wall-modeled Large Eddy Simulation (LES), and Reynolds Averaged Navier-Stokes (RANS) simulations (SST k-ω, v2–f, and Reynolds Stress Model (RSM)) were performed in the same channel geometry. The Wall-Adapting Local Eddy-viscosity SGS mdoel (WALE) [1] is used for the LES calculation. Mean velocities calculated from the RANS and LES were compared with the PIV data. Turbulent kinetic energy budgets were calculated from the experiment, and were compared with the LES and RSM model, highlighting the major shortcomings of RANS models to predict correct heat transfer behavior for the impingement problem. Temperature Sensitive Paint (TSP) was also used to experimentally obtain a local heat transfer distribution at the target and the side walls. An attempt was made to connect the complex aerodynamic flow behavior with results obtained from heat transfer, indicating heat transfer is a manifestation of flow phenomena. The accuracy of LES in predicting the mean flow field, turbulent statistics, and heat transfer is shown in the current work as it is validated against the experimental data through PIV and TSP.

Flow and Heat Transfer Analysis in a Single Row Narrow Impingement Channel: Comparison of Particle Image Velocimetry, Large Eddy Simulation, and RANS to Identify RANS Limitations

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Jahed Hossain ◽  
Erik Fernandez ◽  
Christian Garrett ◽  
Jayanta Kapat
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mean Flow ◽  
Single Row ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics ◽  
Image Velocimetry ◽  
Flow Phenomena ◽  
The Mean

The present study aims to understand the flow, turbulence, and heat transfer in a single row narrow impingement channel for gas turbine heat transfer applications. Since the advent of several advanced manufacturing techniques, narrow wall cooling schemes have become more practical. In this study, the Reynolds number based on jet diameter was ≃15,000, with the jet plate having fixed jet hole diameters and hole spacing. The height of the channel is three times the impingement jet diameter. The channel width is four times the jet diameter of the impingement hole. The dynamics of flow and heat transfer in a single row narrow impingement channel are experimentally and numerically investigated. Particle image velocimetry (PIV) was used to reveal the detailed information of flow phenomena. PIV measurements were taken at a plane normal to the target wall along the jet centerline. The mean velocity field and the turbulent statistics generated from the mean flow field were analyzed. The experimental data from the PIV reveal that the flow is highly anisotropic in a narrow impingement channel. To support experimental data, wall-modeled large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) simulations (shear stress transport k–ω, ν2−f, and Reynolds stress model (RSM)) were performed in the same channel geometry. Mean velocities calculated from the RANS and LES were compared with the PIV data. Turbulent kinetic energy budgets were calculated from the experiment, and were compared with the LES and RSM model, highlighting the major shortcomings of RANS models to predict correct heat transfer behavior for the impingement problem. Temperature-sensitive paint (TSP) was also used to experimentally obtain a local heat transfer distribution at the target and the side walls. An attempt was made to connect the complex aerodynamic flow behavior with the results obtained from heat transfer, indicating heat transfer is a manifestation of flow phenomena. The accuracy of LES in predicting the mean flow field, turbulent statistics, and heat transfer is shown in the current work as it is validated against the experimental data through PIV and TSP.

Effect of Turbulent Intensity and Axial Gap on Turbine Heat Transfer Using Steady and Harmonic Models

2013 ◽  
Author(s):  
Sridhar Murari ◽  
Sunnam Sathish ◽  
Ramakumar Bommisetty ◽  
Jong S. Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Pressure Coefficient ◽  
Heat Transfer Characteristics ◽  
Complex Flow ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Loads

The knowledge of heat loads on the turbine is of great interest to turbine designers. Turbulence intensity and stator-rotor axial gap plays a key role in affecting the heat loads. Flow field and associated heat transfer characteristics in turbines are complex and unsteady. Computational fluid dynamics (CFD) has emerged as a powerful tool for analyzing these complex flow systems. Honeywell has been exploring the use of CFD tools for analysis of flow and heat transfer characteristics of various gas turbine components. The current study has two objectives. The first objective aims at development of CFD methodology by validation. The commercially available CFD code Fine/Turbo is used to validate the predicted results against the benchmark experimental data. Predicted results of pressure coefficient and Stanton number distributions are compared with available experimental data of Dring et al. [1]. The second objective is to investigate the influence of turbulence (0.5% and 10% Tu) and axial gaps (15% and 65% of axial chord) on flow and heat transfer characteristics. Simulations are carried out using both steady state and harmonic models. Turbulence intensity has shown a strong influence on turbine blade heat transfer near the stagnation region, transition and when the turbulent boundary layer is presented. Results show that a mixing plane is not able to capture the flow unsteady features for a small axial gap. Relatively close agreement is obtained with the harmonic model in these situations. Contours of pressure and temperature on the blade surface are presented to understand the behavior of the flow field across the interface.

Large-Eddy Simulation With Zonal Near Wall Treatment of Flow and Heat Transfer in a Ribbed Duct for the Internal Cooling of Turbine Blades

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Sunil Patil ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Large Eddy Simulations ◽  
Internal Cooling ◽  
Mean Flow ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Near Wall

Large eddy simulations of flow and heat transfer in a square ribbed duct with rib height to hydraulic diameter of 0.1 and 0.05 and rib pitch to rib height ratio of 10 and 20 are carried out with the near wall region being modeled with a zonal two layer model. A novel formulation is used for solving the turbulent boundary layer equation for the effective tangential velocity in a generalized co-ordinate system in the near wall zonal treatment. A methodology to model the heat transfer in the zonal near wall layer in the large eddy simulations (LES) framework is presented. This general approach is explained for both Dirichlet and Neumann wall boundary conditions. Reynolds numbers of 20,000 and 60,000 are investigated. Predictions with wall modeled LES are compared with the hydrodynamic and heat transfer experimental data of (Rau et al. 1998, “The Effect of Periodic Ribs on the Local Aerodynamic and Heat Transfer Performance of a Straight Cooling Channel,”ASME J. Turbomach., 120, pp. 368–375). and (Han et al. 1986, “Measurement of Heat Transfer and Pressure Drop in Rectangular Channels With Turbulence Promoters,” NASA Report No. 4015), and wall resolved LES data of Tafti (Tafti, 2004, “Evaluating the Role of Subgrid Stress Modeling in a Ribbed Duct for the Internal Cooling of Turbine Blades,” Int. J. Heat Fluid Flow 26, pp. 92–104). Friction factor, heat transfer coefficient, mean flow as well as turbulent statistics match available data closely with very good accuracy. Wall modeled LES at high Reynolds numbers as presented in this paper reduces the overall computational complexity by factors of 60–140 compared to resolved LES, without any significant loss in accuracy.

On the behaviour of impinging zero-net-mass-flux jets

2016 ◽  
Vol 810 ◽  
pp. 25-59 ◽  
Author(s):  
Carlo Salvatore Greco ◽  
Gennaro Cardone ◽  
Julio Soria
Keyword(s):  
Flow Field ◽  
Vortex Ring ◽  
Strouhal Number ◽  
Mass Flux ◽  
Mean Flow ◽  
Turbulent Statistics ◽  
Image Velocimetry ◽  
The Mean ◽  
Zero Net Mass Flux ◽  
Plate Distance

This paper reports on an experimental study of the influence of the Strouhal number (0.011, 0.022 and 0.044) and orifice-to-plate distances (2, 4 and 6 orifice diameters) on the flow field of an impinging zero-net-mass-flux jet at a Reynolds number equal to 35 000. These jets are generated by a reciprocating piston that oscillates in a cavity behind a circular orifice. Instantaneous two-dimensional in-plane velocity fields are measured in a plane containing the orifice axis using multigrid/multipass cross-correlation digital particle image velocimetry. These measurements have been used to investigate the mean flow quantities and turbulent statistics of the impinging zero-net-mass-flux jets. In addition, the vortex ring behaviour is analysed via its trajectory and azimuthal vorticity as well as the saddle point excursion, the flow rate and entrainment. The behaviour of all these quantities depends on the Strouhal number and the orifice-to-plate distance because the former governs the presence and the relative importance of the vortex ring and the trailing jet on the flow field and the latter delimits the downstream evolution of these structures.

Large-Eddy Simulation With Zonal Near Wall Treatment of Flow and Heat Transfer in a Ribbed Duct for the Internal Cooling of Turbine Blades

2011 ◽  
Author(s):  
Sunil Patil ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Boundary Layer Equation ◽  
Reynolds Numbers ◽  
Wall Region ◽  
Mean Flow ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics ◽  
Wall Boundary Conditions ◽  
Large Eddy ◽  
Near Wall

Large eddy simulations of flow and heat transfer in a square ribbed duct with rib height to hydraulic diameter of 0.1 and 0.05 and rib pitch to rib height ratio of 10 and 20 are carried out with the near wall region being modeled with a zonal two layer model. A novel formulation is used for solving the turbulent boundary layer equation for the effective tangential velocity in a generalized co-ordinate system in the near wall zonal treatment. A methodology to model the heat transfer in the zonal near wall layer in the LES framework is presented. This general approach is explained for both Dirichlet and Neumann wall boundary conditions. Reynolds numbers of 20,000 and 60,000 are investigated. Predictions with wall modeled LES are compared with the hydrodynamic and heat transfer experimental data of Rau et al. [1], and Han et al. [2], and wall resolved LES data of Tafti [3]. Friction factor, heat transfer coefficient, mean flow as well as turbulent statistics match available data closely with very good accuracy. Wall modeled LES at high Reynolds numbers as presented in this paper reduces the overall computational complexity by factors of 60–140 compared to resolved LES, without any significant loss in accuracy.

Flow Visualization Experiment of a Swirling Flow Formed Downstream of a Piping With Successive Three Elbow to be Applied to Divertor Cooling

2014 ◽  
Author(s):  
Shoichi Kodate ◽  
Shinji Ebara ◽  
Hidetoshi Hashizume
Keyword(s):  
Heat Transfer ◽  
Swirling Flow ◽  
Pipe Wall ◽  
Mean Flow ◽  
Transfer Enhancement ◽  
Cooling Systems ◽  
Turbulent Statistics ◽  
Visualization Experiment ◽  
The Mean ◽  
3D Layout

As one of potential divertor cooling systems, three-dimensionally connected elbow piping has been proposed. In this study, a visualization experiment was conducted for swirling flows generated downstream of five kinds of piping with successive three three-dimensionally connected elbows in order to evaluate the applicability of these systems to divertor cooling by comparing with the dual elbow case previously obtained in terms of strength of the swirling flow and turbulent statistics. From the experimental results, it was found that the triple elbow piping in which all elbows were connected three–dimensionally, referred to as 3D+3D layout, generated strong swirling velocity components than those of the dual elbow case and it became up to 70 % of the mean flow velocity. Moreover, it did not attenuate even 5D downstream of the triple elbow, where D was the diameter of the piping and the applicability of this flow field to divertor cooling can be promising. In addition, when heat transfer was evaluated in terms of turbulent statistics in the 3D+3D layout, heat transfer enhancement is expected because larger turbulent kinetic energy was observed near the pipe wall than a straight piping case.

Turbulent flow past a porous plate

1976 ◽  
Vol 73 (3) ◽  
pp. 565-591 ◽  
Author(s):  
J. M. R. Graham
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Turbulent Flow ◽  
Porous Plate ◽  
Lattice Structures ◽  
Extended Version ◽  
Mean Flow ◽  
Flow Past ◽  
Flow Through ◽  
The Mean

The method of Vickery for calculating the drag of plane lattice structures normal to a turbulent stream is extended to cases of increased solidity. The analysis incorporates an extended version of Taylor's theory for the flow through a porous plate, and a simplified version of Hunt's analysis of the distortion of a turbulent flow by the mean flow field of a body. Some comparisons are made with experimental data.

Fundamental Issues and Recent Advancements in Analysis of Aircraft Brake Natural Convective Cooling

1998 ◽  
Vol 120 (4) ◽  
pp. 840-857 ◽  
Author(s):  
M. P. Dyko ◽  
K. Vafai
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Flow Field ◽  
Three Dimensional ◽  
Convective Cooling ◽  
Cooling Flow ◽  
Physical Mechanisms ◽  
Braking System ◽  
Flow And Heat Transfer ◽  
Convection Cooling

A heightened awareness of the importance of natural convective cooling as a driving factor in design and thermal management of aircraft braking systems has emerged in recent years. As a result, increased attention is being devoted to understanding the buoyancy-driven flow and heat transfer occurring within the complex air passageways formed by the wheel and brake components, including the interaction of the internal and external flow fields. Through application of contemporary computational methods in conjunction with thorough experimentation, robust numerical simulations of these three-dimensional processes have been developed and validated. This has provided insight into the fundamental physical mechanisms underlying the flow and yielded the tools necessary for efficient optimization of the cooling process to improve overall thermal performance. In the present work, a brief overview of aircraft brake thermal considerations and formulation of the convection cooling problem are provided. This is followed by a review of studies of natural convection within closed and open-ended annuli and the closely related investigation of inboard and outboard subdomains of the braking system. Relevant studies of natural convection in open rectangular cavities are also discussed. Both experimental and numerical results obtained to date are addressed, with emphasis given to the characteristics of the flow field and the effects of changes in geometric parameters on flow and heat transfer. Findings of a concurrent numerical and experimental investigation of natural convection within the wheel and brake assembly are presented. These results provide, for the first time, a description of the three-dimensional aircraft braking system cooling flow field.

scholarly journals Effects of Temperature on the Flow and Heat Transfer in Gel Fuels: A Numerical Study

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 821
Author(s):  
Qin-Liu Cao ◽  
Wei-Tao Wu ◽  
Wen-He Liao ◽  
Feng Feng ◽  
Mehrdad Massoudi
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Transport System ◽  
Apparent Viscosity ◽  
Thermal Design ◽  
Straight Pipe ◽  
Heating Wall ◽  
Supply Pressure ◽  
Flow And Heat Transfer ◽  
The Mean

In general, rheological properties of gelled fuels change dramatically when temperature changes. In this work, we investigate flow and heat transfer of water-gel in a straight pipe and a tapered injector for non-isothermal conditions, which mimic the situations when gelled fuels are used in propulsion systems. The gel-fluid is modeled as a non-Newtonian fluid, where the viscosity depends on the shear rate and the temperature; a correlation fitted with experimental data is used. For the fully developed flow in a straight pipe with heating, the mean apparent viscosity at the cross section when the temperature is high is only 44% of the case with low temperature; this indicates that it is feasible to control the viscosity of gel fuel by proper thermal design of pipes. For the flow in the typical tapered injector, larger temperature gradients along the radial direction results in a more obvious plug flow; that is, when the fuel is heated the viscosity near the wall is significantly reduced, but the effect is not obvious in the area far away from the wall. Therefore, for the case of the tapered injector, as the temperature of the heating wall increases, the mean apparent viscosity at the outlet decreases first and increases then due to the high viscosity plug formed near the channel center, which encourages further proper design of the injector in future. Furthermore, the layer of low viscosity near the walls plays a role similar to lubrication, thus the supply pressure of the transport system is significantly reduced; the pressure drop for high temperature is only 62% of that of low temperature. It should be noticed that for a propellent system the heating source is almost free; therefore, by introducing a proper thermal design of the transport system, the viscosity of the gelled fuel can be greatly reduced, thus reducing the power input to the supply pressure at a lower cost.

scholarly journals Instability wave models for the near-field fluctuations of turbulent jets

2011 ◽  
Vol 689 ◽  
pp. 97-128 ◽  
Author(s):  
K. Gudmundsson ◽  
Tim Colonius
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Microphone Array ◽  
Near Field ◽  
Turbulent Jets ◽  
Instability Wave ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Scale Structures

AbstractPrevious work has shown that aspects of the evolution of large-scale structures, particularly in forced and transitional mixing layers and jets, can be described by linear and nonlinear stability theories. However, questions persist as to the choice of the basic (steady) flow field to perturb, and the extent to which disturbances in natural (unforced), initially turbulent jets may be modelled with the theory. For unforced jets, identification is made difficult by the lack of a phase reference that would permit a portion of the signal associated with the instability wave to be isolated from other, uncorrelated fluctuations. In this paper, we investigate the extent to which pressure and velocity fluctuations in subsonic, turbulent round jets can be described aslinearperturbations to the mean flow field. The disturbances are expanded about the experimentally measured jet mean flow field, and evolved using linear parabolized stability equations (PSE) that account, in an approximate way, for the weakly non-parallel jet mean flow field. We utilize data from an extensive microphone array that measures pressure fluctuations just outside the jet shear layer to show that, up to an unknown initial disturbance spectrum, the phase, wavelength, and amplitude envelope of convecting wavepackets agree well with PSE solutions at frequencies and azimuthal wavenumbers that can be accurately measured with the array. We next apply the proper orthogonal decomposition to near-field velocity fluctuations measured with particle image velocimetry, and show that the structure of the most energetic modes is also similar to eigenfunctions from the linear theory. Importantly, the amplitudes of the modes inferred from the velocity fluctuations are in reasonable agreement with those identified from the microphone array. The results therefore suggest that, to predict, with reasonable accuracy, the evolution of the largest-scale structures that comprise the most energetic portion of the turbulent spectrum of natural jets, nonlinear effects need only be indirectly accounted for by considering perturbations to the mean turbulent flow field, while neglecting any non-zero frequency disturbance interactions.

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