Boundary-layer velocity profiles in a swirling convergent flow field

1972 ◽  
Vol 52 (2) ◽  
pp. 357-367 ◽  
Author(s):  
T. M. Houlihan ◽  
D. J. Hornstra
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Swirling Flow ◽  
Theoretical Calculations ◽  
Experimental Investigations ◽  
Conical Nozzle ◽  
Flow Conditions ◽  
Boundary Layer Flows ◽  
Layer Velocity ◽  
Convergent Flow

Velocity distributions within the boundary layer of a swirling flow of incompressible fluid in a convergent conical nozzle have been investigated. Theoretical calculations with boundary conditions more appropriate to physically existent situations discounted the existence of 'super-velocities’ within the boundary layer. Parallel experimental investigations demonstrated an interdependence of core and boundary-layer flows which precluded the maintenance of the flow conditions required by the analysis.

Jeffery-Hamel boundary-layer flows over curved beds

1988 ◽  
Vol 186 ◽  
pp. 583-597 ◽  
Author(s):  
P. M. Eagles
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Film Flow ◽  
Local Approximation ◽  
Main Stream ◽  
Streamwise Direction ◽  
Boundary Layer Flows ◽  
Boundary Layer Equations ◽  
First Approximation ◽  
Local Value

We find certain exact solutions of Jeffery-Hamel type for the boundary-layer equations for film flow over certain beds. If β is the angle of the bed with the horizontal and S is the arclength these beds have equation sin β = (const.)S−3, and allow a description of flows on concave and convex beds. The velocity profiles are markedly different from the semi-Poiseuille flow on a plane bed.We also find a class of beds in which the Jeffery-Hamel flows appear as a first approximation throughout the flow field, which is infinite in streamwise extent. Since the parameter γ specifying the Jeffery-Hamel flow varies in the streamwise direction this allows a description of flows over curved beds which are slowly varying, as described in the theory, in such a way that the local approximation is that Jeffery-Hamel flow with the local value of γ. This allows the description of flows with separation and reattachment of the main stream in some cases.

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2020 ◽  
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 2·105) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1D-CTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probe measurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

Computational and experimental investigations in a cyclone dust separator

1997 ◽  
Vol 211 (4) ◽  
pp. 247-257 ◽  
Author(s):  
S M Fraser ◽  
A M Abdel-Razek ◽  
M Z Abdullah
Keyword(s):  
Flow Field ◽  
Richardson Number ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Cyclone Chamber ◽  
Dust Separator

Three-dimensional turbulent flow in a model cyclone has been simulated using PHOENICS code and experimental studies carried out using a laser Doppler anemometry (LDA) system. The experimental results were used to validate the computed velocity distributions based on the standard and a modified k-∊ model. The standard k-∊ model was found to be unsatisfactory for the prediction of the flow field inside the cyclone chamber. By considering the strong swirling flow and the streamlined curvature, a k-∊ model, modified to take account of the Richardson number, provided better velocity distributions and better agreement with the experimental results.

Aeroelasticity at Reversed Flow Conditions: Part 1—Numerical and Experimental Investigations of a Compressor Cascade With Controlled Vibration

2011 ◽  
Author(s):  
Harald Schoenenborn ◽  
Virginie Chenaux ◽  
Peter Ott
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Experimental Investigations ◽  
Blade Surface ◽  
Flow Conditions ◽  
Steady State Flow ◽  
Reversed Flow ◽  
Blow Down

The prediction of flutter and forced response at normal flow conditions has become a standard procedure during the design of compressor airfoils. But at severe off-design conditions, the flow field becomes very complex, especially during the surge blow-down phase where reversed flow conditions occur. The correct prediction of the unsteady pressures and the resulting aerodynamic excitation or damping at these conditions remains an extremely challenging task. In the first part of the paper, basic investigations for these flow conditions are presented. Aeroelastic calculations during compressor surge are shown in the second part. Experimental investigations were performed in the Annular Test Facility for non-rotating cascades at EPF Lausanne. The test cascade was exposed to flow conditions as expected during the surge blow-down phase which is characterized by large separation regions. Measurements of the steady-state flow conditions on the blade surface, at the outer wall, upstream and downstream of the cascade provided detailed information about the steady flow conditions. The cascade was then subjected to controlled vibration of the blades with constant amplitudes and inter-blade phase angles. Unsteady pressure measurements on the blade surface and at the casing wall provided information about the resulting unsteady flow conditions. Analytical CFD calculations were performed. The steady flow field was calculated using a RANS code. Based on the steady-state flow field, unsteady calculations applying a linearized code were carried out. The agreement between measurements and calculations shows that the steady flow as well as the unsteady flow phenomena can be predicted quantitatively. In addition, knowing the blade vibration mode shape, which in this case is a torsion mode, the aerodynamic damping can be determined for the corresponding flow conditions.

Investigations of the Boundary Layer on a Highly Loaded Compressor Cascade With Wake-Induced Transition

2006 ◽  
Author(s):  
Jens Iseler ◽  
Lothar Hilgenfeld ◽  
Michael Pfitzner
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Large Scale ◽  
Quality Data ◽  
Experimental Investigations ◽  
Generation Process ◽  
Unsteady Boundary Layer ◽  
Compressor Cascade ◽  
Boundary Layer Development ◽  
Layer Development

The flow field through a turbomachinery compressor cascades is significantly affected by the unsteady flow originating from the upstream blade rows. The interaction is caused by the wakes from the upstream blades, which affect the properties of the boundary layer of the downstream blades. In addition, pressure fluctuations exist between upstream and downstream blades. These phenomenona play a significant role in the loss generation process on turbomachinery blades because it influences the onset of transition in the boundary layer and has the potential to suppress a boundary layer separation in some cases. Extensive experimental investigations have been performed at the Institute of Jet Propulsion in Neubiberg, where these effects where studied in detail. The measurements were performed on a large scale compressor cascade called V103-220. The chord length of l = 220 mm chosen allowed the unsteady boundary layer development to be studied in great detail and provided high quality data for this complex flow, which can be used for the validation of CFD codes. Unsteady CFD calculations were performed using the RANS-code TRACE developed at DLR Cologne. A modern variant of the Wilcox k-ω turbulence model in combination with a newly implemented transition model was used, allowing a better determination of multimode transition. A multiblock grid with an O-type grid around the blade and a boundary layer resolution of y+<1 was used. Experimental and numerical results confirm that wake passing has a large influence on the unsteady boundary layer development also in this compressor flow case. The premature forced transition is followed by a stable calmed region, which partially suppresses laminar separation due to its higher shear stress level and delays the onset of transition in the path between wakes. In addition, it was found that the leakage from two slots, which are opened in the rig when the wake generator device is installed, changes the flow field considerably. This effect is not fully reproduced by the CFD calculations. To study this effect in more detail, three-dimensional steady and unsteady CFD calculations were undertaken and are being continued.

Effects of Free Stream Turbulence on Intermittent Boundary Layer Flows

1995 ◽  
Author(s):  
Anestis I. Kalfas ◽  
Robin L. Elder
Keyword(s):  
Boundary Layer ◽  
Stream Flow ◽  
Free Stream ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Flow Transition ◽  
Flow Conditions ◽  
Boundary Layer Flows ◽  
Laminar Separation ◽  
Free Stream Turbulence

This paper considers the effects of free stream turbulence intensity on intermittent boundary layer flows related to turbomachinery. The present experimental investigation has been undertaken under free stream flow conditions dominated by grid generated turbulence and Reynolds numbers appropriate for turbomachinery applications. Unseparated flow transition in the boundary layer has been considered using a flat plate with the C4 leading edge which has been designed to avoid laminar separation. This configuration provided the opportunity to study the effect of a realistic turbomachinery leading edge shape on transition. Boundary layer type hot-wire probes have been used in order to acquire detailed information about the effect of the free stream conditions and the leading edge configuration on the structure of the boundary layer. Furthermore, information about the intermittency distribution throughout the boundary layer has been obtained using statistical analysis of the velocity record of the flow field.

Three-dimensional laminar compressible boundary layers with large injection

1975 ◽  
Vol 71 (4) ◽  
pp. 711-727 ◽  
Author(s):  
C. S. Vimala ◽  
G. Nath
Keyword(s):  
Boundary Layer ◽  
Swirling Flow ◽  
Three Dimensional ◽  
Large Mass ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Compressible Boundary Layer ◽  
Boundary Layer Flows ◽  
Compressible Boundary Layers ◽  
Layer Flow

The effect of large mass injection on the following three-dimensional laminar compressible boundary-layer flows is investigated by employing the method of matched asymptotic expansions: (i) swirling flow in a laminar compressible boundary layer over an axisymmetric surface with variable cross-section and (ii) laminar compressible boundary-layer flow over a yawed infinite wing in a hypersonic flow. The resulting equations are solved numerically by combining the finite-difference technique with quasi-linearization. An increase in the swirl parameter, the yaw angle or the wall temperature is found to be capable of bringing the viscous layer nearer the surface and reducing the effects of massive blowing.

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2021 ◽  
pp. 1-12
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 200 000) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1DCTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probemeasurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

Influence of the Swirling Flow in the Side Cavities of a High-Pressure Centrifugal Compressor on the Characteristics of Excited Acoustic Modes

2012 ◽  
Author(s):  
N. Petry ◽  
S. König ◽  
F.-K. Benra
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Swirling Flow ◽  
Frame Of Reference ◽  
Circumferential Velocity ◽  
Experimental Investigations ◽  
Element Analysis ◽  
Acoustic Modes ◽  
At Resonance

Previous experimental investigations revealed the existence of acoustic modes in the side cavities of a high-pressure centrifugal compressor. These modes were excited by pressure patterns which resulted from rotor/stator-interactions (often referred to as Tyler/Sofrin-modes). The acoustic modes were significantly influenced by the prevailing flow in the side cavities. The flow field in such rotor/stator-cavities is characterized by a high circumferential velocity component. The circumferential velocity of the flow and the phase velocity of the acoustic eigenmode superimpose each other, so that the frequencies of the acoustic eigenmodes with respect to the stator frame of reference follow from the sum of both velocities. In the previous study the circumferential velocity was estimated based on existing literature and the phase velocities of the acoustic modes were calculated via an acoustic modal analysis. Based on these results the rotational speeds of the compressor, where acoustic modes were excited in resonance, were determined. The present paper is based on these results and focuses on the influence of the swirling flow and the coupling of the excited acoustic modes between the two side cavities. Such a coupling has been predicted in previous numerical studies but no experimental evidence was available at that time. In this study the circumferential velocities of the flow are determined by measuring the actual radial pressure distribution in the side cavities and assuming radial equilibrium. The determined values are directly used for the prediction of the rotational speeds at resonance. The values for the rotational speeds at resonance predicted that way are compared to the resonance speeds found in the experiments. Further on, simultaneously measured pressure fluctuations in the shroud and hub side cavities with respect to the rotor frame of reference give evidence about the coupling of the acoustic modes between the two side cavities in case of resonance. If the experimentally determined swirling flow velocity is accounted for in the prediction of acoustic resonances, the calculated rotational speeds of resonance are in good agreement with the experimental findings in most cases. Neglecting the flow in the cavities, however, leads to large deviations between calculated and experimentally determined rotational speeds. Varying the operating point of the compressor results in changes of the circumferential velocities in the side cavities and, therefore, in changes of the rotational speeds of resonance. Contrary to the acoustic modes calculated via a Finite Element Analysis by the authors of this paper in previous studies the excited acoustic modes in the experiments are mostly not coupled between the two side cavities, but are localized to one of both cavities. This finding is assumed to be caused by the flow field in the compressor.

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