Effect of Aspect Ratio on Flow Field of Surface-Mounted Obstacles

2005 ◽  
Author(s):  
Rifki Rifki ◽  
M. Javed Khan ◽  
Anwar Ahmed ◽  
Zafar Bangash
Keyword(s):  
Aspect Ratio ◽  
Flow Field

Flow Measurements in a Nozzle Guide Vane Passage With a Low Aspect Ratio and Endwall Contouring

2000 ◽  
Author(s):  
Steven W. Burd ◽  
Terrence W. Simon
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Guide Vane ◽  
Flow Measurements ◽  
Vast Number ◽  
Aspect Ratios ◽  
Nozzle Guide Vane ◽  
Endwall Contouring ◽  
Nozzle Guide

The vast number of turbine cascade studies in the literature has been performed in straight-endwall, high-aspect-ratio, linear cascades. As a result, there has been little appreciation for the role of, and added complexity imposed by, reduced aspect ratios. There also has been little documentation of endwall profiling at these reduced spans. To examine the role of these factors on cascade hydrodynamics, a large-scale nozzle guide vane simulator was constructed at the Heat Transfer Laboratory of the University of Minnesota. This cascade is comprised of three airfoils between one contoured and one flat endwall. The geometries of the airfoils and endwalls, as well as the experimental conditions in the simulator, are representative of those in commercial operation. Measurements with hot-wire anemometry were taken to characterize the flow approaching the cascade. These measurements show that the flow field in this cascade is highly elliptic and influenced by pressure gradients that are established within the cascade. Exit flow field measurements with triple-sensor anemometry and pressure measurements within the cascade indicate that the acceleration imposed by endwall contouring and airfoil turning is able to suppress the size and strength of key secondary flow features. In addition, the flow field near the contoured endwall differs significantly from that adjacent to the straight endwall.

The Effect of a Downstream Rotor on the Measured Performance of a Transonic Turbine Nozzle

1986 ◽  
Vol 108 (2) ◽  
pp. 269-274
Author(s):  
R. G. Williamson ◽  
S. H. Moustapha ◽  
J. P. Huot
Keyword(s):  
Performance Evaluation ◽  
Aspect Ratio ◽  
Flow Field ◽  
Large Scale ◽  
Outer Wall ◽  
Nozzle Flow ◽  
Turning Angle ◽  
Low Aspect Ratio ◽  
Transonic Turbine ◽  
Mach Numbers

Two nozzle designs, involving the same low aspect ratio, high turning angle vanes, and differing in outer wall contour, were tested over a range of exit Mach numbers up to supersonic values. The experiments were conducted on a large-scale, full annular configuration with and without a representative rotor downstream. Nozzle performance was found to be significantly affected by rotor operation, the influence depending on the detailed characteristics of the nozzle flow field, as well as on the design and operation of the rotor itself. It is suggested that performance evaluation of low aspect ratio nozzles of high turning angle may require appropriate testing with a rotor.

Numerical Study of Winglet at Low Reynolds Numbers

2013 ◽  
Author(s):  
Sina Pooladsanj ◽  
Mehran Tadjfar
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Vortex Flow ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Flow Zone ◽  
Low Reynolds Numbers ◽  
Structured Grid ◽  
Flow Field Characteristics ◽  
Wing Aspect Ratio

A numerical study has been performed to evaluate the aerodynamics coefficients of a winglet in the range of Reynolds numbers below 30,000. In this study some parameters on winglet design have been considered. The effect of winglet-tip airfoil thickness has been investigated on aerodynamics coefficients. In order to explore this effect, two different airfoils (NACA0002 and NACA0012) were employed at the winglet-tip. The influence of varying the winglet connection angle to the wing on aerodynamics coefficients and flow field characteristics in the vortex flow zone such as; circulation magnitude and vorticity magnitude in the vortex core have been studied. Six connection angles including 20°, 30°, 40°, 50°, 60° and 70° have been studied. Negative values of these angles have also been considered. In addition, the effect of changing wing aspect ratio on aerodynamics coefficients has been investigated. To solve the flow field around the studied geometry a fully structured grid was used which consists of 84 blocks.

Response Dynamics of Recirculation Structures in Coaxial Nonpremixed Swirl-Stabilized Flames Subjected to Acoustic Forcing

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Uyi Idahosa ◽  
R. Santhosh ◽  
Ankur Miglani ◽  
Saptarshi Basu
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Fluid Dynamic ◽  
High Energy ◽  
Reacting Flow ◽  
Flow State ◽  
Response Dynamics ◽  
Jet Flame ◽  
Flame Response ◽  
Acoustic Forcing

This paper reports the time-mean and phase-locked response of nonreacting as well as reacting flow field in a coaxial swirling jet/flame (nonpremixed). Two distinct swirl intensities plus two different central pipe flow rates at each swirl setting are investigated. The maximum response is observed at the 105 Hz mode in the range of excitation frequencies (0–315 Hz). The flow/flame exhibited minimal response beyond 300 Hz. It is seen that the aspect ratio change of inner recirculation zone (IRZ) under nonreacting conditions (at responsive modes) manifests as a corresponding increase in the time-mean flame aspect ratio. This is corroborated by ∼25% decrease in the IRZ transverse width in both flame and cold flow states. In addition, 105 Hz excited states are found to shed high energy regions (eddies) asymmetrically when compared to dormant 315 Hz pulsing frequency. The kinetic energy (KE) of the flow field is subsequently reduced due to acoustic excitation and a corresponding increase (∼O (1)) in fluctuation intensity is witnessed. The lower swirl intensity case is found to be more responsive than the high swirl case as in the former flow state the resistance offered by IRZ to incoming acoustic perturbations is lower due to inherently low inertia. Next, the phase-locked analysis of flow and flame structure is employed to further investigate the phase dependence of flow/flame response. It is found that the asymmetric shifting of IRZ mainly results at 270 deg acoustic forcing. The 90 deg phase angle forcing is observed to convect the IRZ farther downstream in both swirl cases as compared to other phase angles. The present work aims primarily at providing a fluid dynamic view point to the observed nonpremixed flame response without considering the confinement effects.

scholarly journals Investigation of the Three-Dimensional Flow Field Within a Transonic Fan Rotor: Experiment and Analysis

1985 ◽  
Vol 107 (2) ◽  
pp. 436-448 ◽  
Author(s):  
M. J. Pierzga ◽  
J. R. Wood
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Numerical Technique ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Flow ◽  
Data Matrix ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Finite Volume Approach

An experimental investigation of the three-dimensional flow field through a low aspect ratio, transonic, axial-flow fan rotor has been conducted using an advanced laser anemometer (LA) system. Laser velocimeter measurements of the rotor flow field at the design operating speed and over a range of through flow conditions are compared to analytical solutions. The numerical technique used herein yields the solution to the full, three-dimensional, unsteady Euler equations using an explicit time-marching, finite volume approach. The numerical analysis, when coupled with a simplified boundary layer calculation, generally yields good agreement with the experimental data. The test rotor has an aspect ratio of 1.56, a design total pressure ratio of 1.629 and a tip relative Mach number of 1.38. The high spatial resolution of the LA data matrix (9 radial × 30 axial × 50 blade-to-blade) permits details of the transonic flow field such as shock location, turning distribution, and blade loading levels to be investigated an compared to analytical results.

The relation between losses and entry-flow conditions in short dump diffusers for combustors

1988 ◽  
Vol 92 (920) ◽  
pp. 390-396 ◽  
Author(s):  
A. Klein
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Radial Direction ◽  
Flow Conditions ◽  
Compressor Blades ◽  
Inlet Flow ◽  
Jet Engine ◽  
Satisfactory Degree ◽  
Blockage Factor ◽  
Experimental Correlation

SummaryAn experimental correlation is presented between the losses and the inlet flow conditions in short dump diffusers for turbojet combustors. Cascades of compressor blades upstream of the diffuser were used to make the flow field at inlet similar to that in a real jet engine. The flow field was altered in two ways — by varying the distance between the cascades and the diffuser inlet plane and by changing the blade aspect ratio. The measurements show clearly that distortions in the radial direction affect the losses to a much larger extent than non-uniformities in the circumferential direction. In consequence, the performance can be correlated to a satisfactory degree of accuracy simply by using the radial blockage factor at inlet.

Performance Prediction for High Turning Low Aspect Ratio Stator Cascades in the Transonic Regime

1970 ◽  
Vol 92 (4) ◽  
pp. 390-398
Author(s):  
H. F. L. Griepentrog
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Flow Field ◽  
Performance Prediction ◽  
Transonic Flow ◽  
Secondary Flows ◽  
Compressor Stage ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Boundary Layer Interaction

This paper describes a method for the prediction of the transonic flow field in a high solidity, high turning cascade, suitable for use as stator of a shock-in-rotor supersonic compressor stage. Effects of shock boundary layer interaction is taken into account by empirical correlation, valid for blade aspect ratios below unity. Use of partial slots for reduction of the secondary flows is briefly discussed and a correlation on slot efficiency is presented.

The Flow Field Distribution of Subsurface Flow Constructed Wetlands

2013 ◽  
Vol 448-453 ◽  
pp. 472-477
Author(s):  
Quan Wang ◽  
Zhi Xin Song ◽  
Shao Yuan Bai
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Field Distribution ◽  
Constructed Wetlands ◽  
Matrix Material ◽  
Subsurface Flow ◽  
Growth Effect ◽  
Utilization Rate ◽  
Substrate Thickness ◽  
Subsurface Flow Constructed Wetlands

this paper reviewed the progress of flow field distribution in subsurface flow constructed wetlands (SSF), generalized the theoretical basis for numerical simulation of flow field distribution and the application of computer software in subsurface flow constructed wetlands. At the same time, analysed the relationship of flow field distribution with the bed body of aspect ratio, substrate thickness, material properties of matrix and the way of filling, found that the appropriate aspect ratio, substrate thickness and scientific way of filling could improve the flow field distribution, which was an effective way to improve the utilization rate of substrate. In addition, summarized the plant roots system and microbe growth effect on the flow field distribution. Therefore, the flow field distribution was directly effected of utilization ratio of matrix material, and living environmental condition of microbe, thus the flow field distribution as a parameter for design would be a kind of scientific method. Finally, proposed the corresponding research methods, and discussed how to improve the flow field distribution uniform, for improving the design level of subsurface flow constructed wetlands.

Simulation on the Flow Field of Mini-Hydrocyclones for Different Inlet Sizes

2013 ◽  
Vol 864-867 ◽  
pp. 1183-1191 ◽  
Author(s):  
Chao Yan ◽  
Qiang Yang ◽  
Hua Lin Wang
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Solid Particles ◽  
Design And Optimization ◽  
Fluent Software ◽  
Simulation Results ◽  
Shape And Size

This paper aims to improve the separation of fine solid particles in mini-hydrocyclones by changing the shape and size of the mini-hydrocyclone inlet. This study also examines the best mini-hydrocyclone inlet shape and size. Fluent software is used to simulate the flow field of the continuous and dispersion phases in different mini-hydrocyclone. The simulation results can guide the design and optimization of mini-hydrocyclones and determine the optimum inlet aspect ratio.

Simulation of Three-Dimensional Viscous Flow Within a Multistage Turbine

1990 ◽  
Vol 112 (3) ◽  
pp. 370-376 ◽  
Author(s):  
J. J. Adamczyk ◽  
M. L. Celestina ◽  
T. A. Beach ◽  
M. Barnett
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Three Dimensional ◽  
Equation System ◽  
Aerodynamic Performance ◽  
Experimental Measurements ◽  
Low Aspect Ratio ◽  
Blade Row ◽  
Multistage Turbine ◽  
Secondary Flow Field

This work outlines a procedure for simulating the flow field within multistage turbomachinery, which includes the effects of unsteadiness, compressibility, and viscosity. The associated modeling equations are the average passage equation system, which governs the time-averaged flow field within a typical passage of a blade row embedded within a multistage configuration. The results from a simulation of a low aspect ratio stage and one-half turbine will be presented and compared with experimental measurements. It will be shown that the secondary flow field generated by the rotor causes the aerodynamic performance of the downstream vane to be significantly different from that of an isolated blade row.

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