Large Eddy Simulation of Film Cooling Flow From an Inclined Cylindrical Jet

2003 ◽  
Vol 125 (4) ◽  
pp. 734-742 ◽  
Author(s):  
Mayank Tyagi ◽  
Sumanta Acharya
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Wake Region ◽  
Complex Flow ◽  
Mixing Processes ◽  
Hairpin Vortices ◽  
Flow Measurements ◽  
Large Eddy

Predictions of turbine blade film cooling have traditionally employed Reynolds-averaged Navier-Stokes solvers and two-equation models for turbulence. Evaluation of several versions of such models have revealed that the existing two-equation models fail to resolve the anisotropy and the dynamics of the highly complex flow field created by the jet-crossflow interaction. A more accurate prediction of the flow field can be obtained from large eddy simulations (LES) where the dynamics of the larger scales in the flow are directly resolved. In the present paper, such an approach has been used, and results are presented for a row of inclined cylindrical holes at blowing ratios of 0.5 and 1 and Reynolds numbers of 11,100 and 22,200, respectively, based on the jet velocity and hole diameter. Comparison of the time-averaged LES predictions with the flow measurements of Lavrich and Chiappetta (UTRC Report No. 90-04) shows that LES is able to predict the flow field with reasonable accuracy. The unsteady three-dimensional flow field is shown to be dominated by packets of hairpin-shaped vortices. The dynamics of the hairpin vortices in the wake region of the injected jet and their influence on the unsteady wall heat transfer are presented. Generation of “hot spots” and their migration on the film-cooled surface are associated with the entrainment induced by the hairpin structures. Several geometric properties of a “mixing interface” around hairpin coherent structures are presented to illustrate and quantify their impact on the entrainment rates and mixing processes in the wake region.

Large Eddy Simulation of Film Cooling Flow From an Inclined Cylindrical Jet

2003 ◽  
Author(s):  
Sumanta Acharya ◽  
Mayank Tyagi
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Wake Region ◽  
Complex Flow ◽  
Mixing Processes ◽  
Hairpin Vortices ◽  
Flow Measurements ◽  
Large Eddy

Predictions of turbine blade film cooling have traditionally employed Reynolds averaged Navier Stokes (RANS) solvers and two-equation models for turbulence. Evaluation of several versions of such models have revealed that the existing two equation models fail to resolve the anisotropy and the dynamics of the highly complex flow field created by the jet-crossflow interaction. A more accurate prediction of the flow field can be obtained from large eddy simulations (LES) where the dynamics of the larger scales in the flow are directly resolved. In the present paper, such an approach has been used, and results are presented for a row of inclined cylindrical holes at blowing ratios of 0.5 and 1, and a Reynolds number of 11100 and 22200 respectively based on the jet velocity and hole diameter. Comparison of the time-averaged LES predictions with the flow measurements of Lavrich and Chiappetta [1] shows that LES is able to predict the flow field with reasonable accuracy. The unsteady three-dimensional flow field is shown to be dominated by packets of hairpin shaped vortices. The dynamics of the hairpin vortices in the wake region of the injected jet and their influence on the unsteady wall heat transfer is presented. Generation of “hot spots” and their migration on the film-cooled surface is associated with the entrainment induced by the hairpin structures. Several geometric properties of a “mixing interface” around hairpin coherent structures are presented to illustrate and quantify their impact on the entrainment rates and mixing processes in the wake region.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1996 ◽  
Vol 118 (4) ◽  
pp. 835-843 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stator at several operating conditions. The flow field is found to be highly three dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier–Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

Discrete-Jet Film Cooling: A Comparison of Computational Results With Experiments

1994 ◽  
Vol 116 (3) ◽  
pp. 358-368 ◽  
Author(s):  
J. H. Leylek ◽  
R. D. Zerkle
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Navier Stokes ◽  
Complex Flow ◽  
Coupled Flow ◽  
Injection Angle ◽  
Computational Analyses

Large-scale computational analyses have been conducted and results compared with experiments to understand coolant jet and crossflow interaction in discrete-jet film cooling. Detailed three-dimensional elliptic Navier–Stokes solutions, with high-order turbuence modeling, are presented for film cooling using a new model enabling simultaneous solution of fully coupled flow in plenum, film-hole, and cross-stream regions. Computations are carried out for the following range of film cooling parameters typically found in gas turbine airfoil applications: single row of jets with a film-hole length-to-diameter ratio of 1.75 and 3.5; blowing ratio from 0.5 up to 2; coolant-to-crossflow density ratio of 2; streamwise injection angle of 35 deg; and pitch-to-diameter ratio of 3. Comparison of computational solutions with experimental data give good agreement. Moreover, the current results complement experiments and support previous interpretations of measured data and flow visualization. The results also explain important aspects of film cooling, such as the development of complex flow within the film-hole in addition to the well-known counterrotating vortex structure in the cross-stream.

Design and Off-Design Numerical Investigation of a Transonic Double-Splitter Centrifugal Compressor

2008 ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Seiichi Ibaraki
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Cross Sections ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Complex Flow ◽  
Flow Measurements ◽  
Vaned Diffuser

The flow field of a high pressure ratio centrifugal compressor for turbocharger applications is investigated using a three-dimensional Navier-Stokes solver. The compressor is composed of a double-splitter impeller followed by a vaned diffuser. The flow field of the transonic open-shrouded impeller is highly three-dimensional, and it is influenced by shock waves, tip leakage vortices and secondary flows. Their interactions generate complex flow structures which are convected and distorted through the impeller blades. Both steady and unsteady computations are performed in order to understand the physical mechanisms which govern the impeller flow field while the operation ranges from choke to surge. Detailed Laser Doppler Velocimetry (LDV) flow measurements are available at various cross-sections inside the impeller blades at both design and off-design operating conditions.

Numerical Investigation of a Transonic Centrifugal Compressor

2006 ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Seiichi Ibaraki
Keyword(s):  
Shock Waves ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Tip Clearance ◽  
Complex Flow ◽  
Low Velocity ◽  
Flow Measurements

A three-dimensional Navier-Stokes solver is used to investigate the flow field of a high pressure ratio centrifugal compressor for turbocharger applications. Such a compressor consists of a double-splitter impeller followed by a vane diffuser. The inlet flow to the open shrouded impeller is transonic, thus giving rise to interactions between shock waves and boundary layers and between shock waves and tip leakage vortices. These interactions generate complex flow structures which are convected and distorted through the impeller blades. Detailed Laser Doppler Velocimetry (LDV) flow measurements are available at various cross sections inside the impeller blades highlighting the presence of low velocity flow regions near the shroud. Particular attention is focused on understanding the physical mechanisms which govern the flow phenomena in the near shroud region. To this end numerical investigations are performed using different tip clearance modelizations and various turbulence models, and their impact on the computed flow field is discussed.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1994 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stat or at several operating conditions. The flow field is found to be highly three-dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier-Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

Numerical Analysis of the Vaned Diffuser of a Transonic Centrifugal Compressor

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Seiichi Ibaraki
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flow Measurements ◽  
Vaned Diffuser ◽  
High Pressure Ratio ◽  
Unsteady Interaction ◽  
Inlet Conditions

A three-dimensional Navier–Stokes solver is used to investigate the flow field of a high pressure ratio centrifugal compressor for turbocharger applications. Such a compressor consists of a double-splitter impeller followed by a vaned diffuser. Particular attention is focused on the analysis of the vaned diffuser, designed for high subsonic inlet conditions. The diffuser is characterized by a complex three-dimensional flow field and influenced by the unsteady interaction with the impeller. Detailed particle image velocimetry flow measurements within the diffuser are available for comparison purposes.

Numerical Analysis of the Vaned Diffuser of a Transonic Centrifugal Compressor

2007 ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Seiichi Ibaraki
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flow Measurements ◽  
Vaned Diffuser ◽  
High Pressure Ratio ◽  
Unsteady Interaction ◽  
Inlet Conditions

A three-dimensional Navier-Stokes solver is used to investigate the flow field of a high pressure ratio centrifugal compressor for turbocharger applications. Such a compressor consists of a double-splitter impeller followed by a vaned diffuser. Particular attention is focused on the analysis of the vaned diffuser, designed for high subsonic inlet conditions. The diffuser is characterized by a complex three-dimensional flow field, and influenced by the unsteady interaction with the impeller. Detailed Particle Image Velocimetry (PIV) flow measurements within the diffuser are available for comparison purposes.

Numerical Simulation of the Flow Field Around Supersonic Air-Intakes

1994 ◽  
Vol 116 (1) ◽  
pp. 116-123 ◽  
Author(s):  
G. Freskos ◽  
O. Penanhoat
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Complex Flow ◽  
Grid Approach ◽  
Entire Flow ◽  
Flow Configurations ◽  
Cost Efficient

The demand for efficiency in today’s and in future civil aircraft is such that experimental studies alone do not suffice to optimize aircraft aerodynamics. In this context, much effort has been spent in the past decade to develop numerical methods capable of reproducing the phenomena that occur in the engine flow field. This paper presents some studies in Computational Fluid Dynamics related to supersonic inlets. Two approaches are considered. First, there is a need for a code capable of calculating in a cost-efficient way the entire flow field around a two-dimensional or three-dimensional inlet, e.g., to perform parametric studies. To this effect, a computing method based on grid construction by mesh generator dedicated to inlet shapes and on the discretization of the unsteady Euler equations with an explicit upwind scheme was developed. The treatment of complex geometries led us to adopt a multiblock grid approach. Therefore particular attention was paid to the treatment of the boundary conditions between the different domains. Second, there is a need for a code that can capture local phenomena in order to get a better understanding of inlet behavior (shock/shock, shock/boundary layer interactions, etc.). To this effect a two-dimensional turbulent Navier-Stokes code is used. The two-equation k-ε turbulence model included in the program seems to be one of the most successful models for calculating flow realistically. Correction of the near-wall influence extends its capability to complex flow configurations, e.g., those with separated zones.

Validation of a Navier-Stokes Solver for CFD Computations of Transonic Compressors

2006 ◽  
Author(s):  
Roberto Biollo ◽  
Ernesto Benini
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Test Case ◽  
Complex Flow

The progress of numerical methods and computing facilities has led to using Computational Fluid Dynamics (CFD) as a current tool for designing components of gas turbine engines. It is known, however, that a sophisticated numerical model is required to well reproduce the many complex flow phenomena which characterize compression systems, such as shock waves and their interactions with boundary layers and tip clearance flows. In this work, the flow field inside the NASA Rotor 37, a well known test case representative of complex three-dimensional viscous flow structures in transonic bladings, was simulated using a commercial CFD code based on the 3-D Reynolds-averaged Navier-Stokes equations. In order to improve the accuracy of predictions, different aspects of the numerical model were analyzed; in particular, an attempt was made to understand the influence of grid topology, number of nodes and their distribution, turbulence model, and discretization scheme of numerical solution on the accuracy of computed results. Existing experimental data were used to assess the quality of the solutions. The obtainment of a good agreement between computed and measured performance maps and downstream profiles was clearly shown. Also, detailed comparisons with experimental results indicated that the overall features of the three-dimensional shock structure, the shock-boundary layer interaction, and the wake development can be calculated very well in the numerical approach for all the operating conditions. The possibility for a numerical model to better understand the aerodynamic behaviour of existing transonic compressors and to help the design of new configurations was demonstrated. It was also pointed out that the development of an accurate model requires the knowledge of both the physical phenomena place within the flow field and the features of the code which model them.

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