Use of Subdomains for Inverse Problems in Branching Flow Passages

1992 ◽  
Author(s):  
S. Krishnan ◽  
Ajay K. Agrawal ◽  
Tah-teh Yang
Keyword(s):  
Inverse Problems ◽  
Pressure Distribution ◽  
Incompressible Flows ◽  
Wall Pressure ◽  
Calculation Procedure ◽  
Navier Stokes ◽  
Main Duct ◽  
Complex Flow ◽  
Numerical Predictions ◽  
Branching Flow

For inverse problems in complex flow passages, a calculation procedure based on multizone Navier-Stokes method was developed. A heuristic approach was employed to derive wall shape corrections from the wall pressure error. Only two subdomains sharing a row of control volumes were used in the present work. The grid work in the common region was identical for both subdomains. The flow solver, inverse calculation procedure, multizone Navier-Stokes method and subdomain inverse calculation procedure were validated independently against experimental data or numerical predictions. The subdomain inverse calculation method was applied to determine the wall shape of the main duct of a branching flow passage. This main duct was to minimize the pressure gradient downstream of the sidebranch. Inverse calculations resulted in a range of wall shapes with wall pressure distribution approaching the design (prescribed) wall pressure distribution. The present approach was illustrated for laminar, incompressible flows in branching passages. However, the method presented is flexible and can be extended for inverse turbulent flow calculations in multiply connected domains.

Use of Subdomains for Inverse Problems in Branching Flow Passages

1993 ◽  
Vol 115 (2) ◽  
pp. 227-232 ◽  
Author(s):  
Ajay K. Agrawal ◽  
S. Krishnan ◽  
Tah-teh Yang
Keyword(s):  
Inverse Problems ◽  
Pressure Distribution ◽  
Turbulent Flows ◽  
Incompressible Flows ◽  
Wall Pressure ◽  
Calculation Procedure ◽  
Navier Stokes ◽  
Complex Flow ◽  
Numerical Predictions ◽  
Branching Flow

For inverse problems in complex flow passages, a calculation procedure based on a multizone Navier-Stokes method was developed. A heuristic approach was employed to derive wall shape corrections from the wall pressure error. Only two subdomains sharing a row of control volumes were used. The grid work in the common region was identical for both subdomains. The flow solver, inverse calculation procedure, multizone Navier-Stokes method and subdomain inverse calculation procedure were validated independently against experimental data or numerical predictions. Then, the subdomain inverse calculation method was used to determine the wall shape of the main duct of a branching flow passage. A slightly adverse pressure gradient was prescribed downstream of the sidebranch. Inverse calculations resulted in a curved wall diffuser for which the wall pressure distribution matched the design (prescribed) wall pressure distribution. The present method was illustrated for laminar, incompressible flows in branching passages. However, the method presented is flexible and can be extended for turbulent flows in multiply connected domains.

scholarly journals Numerical Calculations of a Turbine Volute Using a 3-D Navier-Stokes Solver

1996 ◽  
Author(s):  
R. F. Martinez-Botas ◽  
K. R. Pullen ◽  
F. Shi
Keyword(s):  
Three Dimensional ◽  
Circular Cross Section ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Complex Flow ◽  
Numerical Predictions ◽  
Flow Features ◽  
Simplec Algorithm ◽  
Complicated Geometry ◽  
High Reynolds

The turbine volute is a complex flow device, about which a few papers on both measurements and CFD predictions have appeared. The main reasons for the difficulties being the complicated geometry which hinders measurements to be taken by both intrusive and non-intrusive techniques, and makes the numerical predictions difficult. In this paper, the complex three-dimensional flow through a turbine volute with non-symmetric circular cross-section is studied by using a 3-D Navier-Stokes solver which has been developed by the authors. In this solver, the fully 3-D Reynolds averaged N-S equations coupled with high Reynolds number k-ε turbulence model together with the wall function under arbitrary curvilinear coordinate system are solved. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLEC algorithm) with the non-staggered grid arrangement is used. In order to eliminate the decoupling between the velocity and pressure under non-staggered grid system, the physical covariant velocity component is selected as dependent variable in momentum equations and a momentum interpolation approach is employed. The validity of the free-vortex assumption is reviewed. The computation results are compared with a set of experiments performed previously by one of the authors. The flow features in the volute are discussed.

Passive Effusion Cooling in a Rectangular S-Bend Diffuser

2012 ◽  
Author(s):  
B. C. N. Ng ◽  
A. M. Birk
Keyword(s):  
Experimental Study ◽  
Pressure Distribution ◽  
Back Pressure ◽  
Wall Pressure ◽  
Flow Conditions ◽  
Complex Flow ◽  
Atmospheric Flow ◽  
Pressure Distributions ◽  
Outlet Flow ◽  
Recovery Performance

The experimental study considered passive effusion cooling in an S-bend diffusing passage in which ambient cool air was drawn naturally into the S-duct passage with sub-atmospheric flow distributions. Seven-hole pressure probes were used to measure the test section’s inlet and outlet flow conditions that were used to evaluate the performance of the S-bend diffuser. Back-pressure, outlet flow-fields and wall pressure distributions were investigated to study the effects of effusion cooling on the pressure recovery performance of the S-bend diffuser. The study revealed a substantial back-pressure penalty and wall pressure distribution alteration in the S-bend passage with full coverage effusion cooling. The outlet diffuser was shown to be not as effective with effusion cooling. The findings highlighted the importance of the design of effusion holes locations in complex flow passages.

Passive Effusion Cooling in a Rectangular S-Bend Diffuser

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
B. C. N. Ng ◽  
A. M. Birk
Keyword(s):  
Experimental Study ◽  
Pressure Distribution ◽  
Back Pressure ◽  
Wall Pressure ◽  
Flow Conditions ◽  
Complex Flow ◽  
Hole Pressure ◽  
Pressure Distributions ◽  
Outlet Flow ◽  
Recovery Performance

The experimental study considered passive effusion cooling in an S-bend diffusing passage in which ambient cool air was drawn naturally into the S-bend passage with subatmospheric flow distributions. Seven-hole pressure probes were used to measure the test section’s inlet and outlet flow conditions which were used to evaluate the performance of the S-bend diffuser. Back-pressure, outlet flow-fields, and wall pressure distributions were investigated to study the effects of effusion cooling on the pressure recovery performance of the S-bend diffuser. The study revealed a substantial back-pressure penalty and wall pressure distribution alteration in the S-bend passage with full coverage effusion cooling. The outlet diffuser was shown to be not as effective with effusion cooling. The findings highlighted the importance of the design of effusion holes locations in complex flow passages.

All Speed and High-Resolution Scheme Applied to Three-Dimensional Multi-Block Complex Flowfield System

2004 ◽  
Vol 20 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Uzu- Kuei Hsu ◽  
Chang- Hsien Tai ◽  
Chien- Hsiung Tsai
Keyword(s):  
Steady State ◽  
Incompressible Flows ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Diffusion Flux ◽  
Time Derivative ◽  
Splitting Method ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Complex Flow

ABSTRACTThe improved numerical approach is implemented with preconditioned Navier-Stokes solver on arbitrary three-dimensional (3-D) structured multi-block complex flowfield. With the successful application of time-derivative preconditioning, present hybrid finite volume solver is performed to obtain the steady state solutions in compressible and incompressible flows. This solver which combined the adjective upwind splitting method (AUSM) family of low-diffusion flux-splitting scheme with an optimally smoothing multistage scheme and the time-derivative preconditioning is used to solve both the compressible and incompressible Euler and Navier-Stokes equations. In addition, a smoothing procedure is used to provide a mechanism for controlling the numerical implementation to avoid the instability at stagnation and sonic region. The effects of preconditioning on accuracy and convergence to the steady state of the numerical solutions are presented. There are two validation cases and three complex cases simulated as shown in this study. The numerical results obtained for inviscid and viscous two-dimensional flows over a NACA0012 airfoil at free stream Mach number ranging from 0.1 to 1.0E-7 indicates that efficient computations of flows with very low Mach numbers are now possible, without losing accuracy. And it is effectively to simulate 3-D complex flow phenomenon from compressible flow to incompressible by using the advanced numerical methods.

Experimental and Numerical Verification of an Optimization of a Fast Rotating High-Performance Radial Compressor Impeller

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
M. Elfert ◽  
A. Weber ◽  
D. Wittrock ◽  
A. Peters ◽  
C. Voss ◽  
...  
Keyword(s):  
High Performance ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Numerical Verification ◽  
Complex Flow ◽  
Radial Compressor ◽  
Wall Functions ◽  
Numerical Predictions ◽  
Compressor Design

An optimization has been performed on a well-proven radial compressor design known as the SRV4 impeller (the Krain impeller), which has been extensively tested in the past, using the autoopti tool developed at DLR's Institute of Propulsion Technology. This tool has shown its capability in several tasks, mainly for axial compressor and fan design as well as for turbine design. The optimization package autoopti was applied to the redesign and optimization of a radial compressor stage with a vaneless diffusor. This optimization was performed for the SRV4 compressor geometry without fillets using a relatively coarse structured mesh in combination with wall functions. The impeller geometry deduced by the optimization had to be slightly modified due to manufacturing constraints. In order to filter out the improvements of the new so-called SRV5 radial compressor design, two work packages were conducted: The first one was the manufacturing of the new impeller and its installation on a test rig to investigate the complex flow inside the machine. The aim was, first of all, the evaluation of a classical performance map and the efficiency chart achieved by the new compressor design. The efficiencies realized in the performance chart were enhanced by nearly 1.5%. A 5% higher maximum mass flow rate was measured in agreement with the Reynolds-averaged Navier–Stokes (RANS) simulations during the design process. The second work package comprises the computational fluid dynamics (CFD) analysis. The numerical investigations were conducted with the exact geometries of both the baseline SRV4 as well as the optimized SRV5 impeller including the exact fillet geometries. To enhance the prediction accuracy of pressure ratio and impeller efficiency, the geometries were discretized by high-resolution meshes of approximately 5 × 106 cells. For the blade walls as well as for the hub region, the mesh resolution allows a low-Reynolds approach in order to get high-quality results. The comparison of the numerical predictions and the experimental results shows a very good agreement and confirms the improvement of the compressor performance using the optimization tool autoopti.

Using Viscous Calculations in Pump Design

1990 ◽  
Vol 112 (3) ◽  
pp. 272-280 ◽  
Author(s):  
F. Martelli ◽  
V. Michelassi
Keyword(s):  
High Performance ◽  
Incompressible Flows ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Code ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Viscous Effects ◽  
Complex Flow ◽  
Pump Design

A viscous computer code for designing the meridional channels of high-performance pumps is presented. An averaging technique is used to reduce the three-dimensional flow to a two-dimensional model. The code, based upon an implicit finite difference method for steady two-dimensional incompressible flows, was validated in complex flow geometries prior to application in the design analysis of an actual pump. Viscous effects are taken into account by two different turbulence models. The Navier-Stokes solver is used in conjunction with a standard blade-to-blade calculation by means of an automatic graphic procedure that exchanges geometric and flowfield data. Various meridional shape solutions are presented and discussed in relation to physical evidence.

scholarly journals Comparison of Heat Transfer Measurements With Computations for Turbulent Flow Around a 180 Degree Bend

1991 ◽  
Author(s):  
D. L. Besserman ◽  
S. Tanrikut
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Navier Stokes ◽  
Complex Flow ◽  
Wall Functions ◽  
Numerical Predictions ◽  
Fully Developed Turbulent Flow

Results of detailed heat transfer measurements are presented for all four walls of a 180° 1:1 aspect ratio duct. Experiments using a transient heat transfer technique with liquid crystal thermography were conducted for turbulent flow over a Reynolds numbers range of 12,500–50,000. Computational results using a Navier-Stokes code are also presented to complement the experiments. Two near-wall shear-stress treatments (wall functions and the two layer wall integration method) were evaluated in conjunction with k-ε formulation of turbulence to assess their ability to predict high local gradients in heat transfer. Results showed that heat transfer on the convex and concave walls is a manifestation of the complex flow field created by the 180° bend. For the flat walls, the streamwise average Nusselt number increases to approximately two times the fully developed turbulent flow value. Ninety degrees into the bend, the importance of the cross-stream gradients is evident with the Nusselt number varying from approximately one to three times the fully developed turbulent flow value. The numerical predictions with two-layer wall integration k-ε turbulence model show very good agreement with the experimental data. These results reinforce the need to accurately predict local heat transfer rates in cooling passages of advanced turbine airfoils to enhance the durability of these components.

Comparison of Heat Transfer Measurements With Computations for Turbulent Flow Around a 180 deg Bend

1992 ◽  
Vol 114 (4) ◽  
pp. 865-871 ◽  
Author(s):  
D. L. Besserman ◽  
S. Tanrikut
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Navier Stokes ◽  
Complex Flow ◽  
Wall Functions ◽  
Numerical Predictions ◽  
Fully Developed Turbulent Flow

Results of detailed heat transfer measurements are presented for all four walls of a 180 deg 1:1 aspect ratio duct. Experiments using a transient heat transfer technique with liquid crystal thermography were conducted for turbulent flow over a Reynolds numbers range of 12,500–50,000. Computational results using a Navier–Stokes code are also presented to complement the experiments. Two near-wall shear-stress treatments (wall functions and the two layer wall integration method) were evaluated in conjunction with k–ε formulation of turbulence to assess their ability to predict high local gradients in heat transfer. Results showed that heat transfer on the convex and concave walls is a manifestation of the complex flow field created by the 180 deg bend. For the flat walls, the streamwise average Nusselt number increases to approximately two times the fully developed turbulent flow value. Ninety degrees into the bend, the importance of the cross-stream gradients is evident with the Nusselt number varying from approximately one to three times the fully developed turbulent flow value. The numerical predictions with two-layer wall integration k–ε turbulence model show very good agreement with the experimental data. These results reinforce the need to predict local heat transfer rates accurately in cooling passages of advanced turbine airfoils to enhance the durability of these components.

Numerical solution of the reduced Navier-Stokes equations for internal incompressible flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1603-1614
Author(s):  
Martin Scholtysik ◽  
Bernhard Mueller ◽  
Torstein K. Fannelop
Keyword(s):  
Numerical Solution ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations
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