Flow in a Rectangular Diffuser With Local Flow Detachment in the Corner Region

1983 ◽  
Vol 105 (2) ◽  
pp. 204-211 ◽  
Author(s):  
F. B. Gessner ◽  
Y. L. Chan
Keyword(s):  
Three Dimensional ◽  
Mean Velocity ◽  
Local Flow ◽  
Flow Angle ◽  
Corner Region ◽  
Streamwise Location ◽  
Angle Data ◽  
Oil Flow ◽  
Attached Flow ◽  
Corner Flows

An experimental study was conducted in order to examine the nature of flow within a high-inlet-aspect-ratio rectangular diffuser with locally detached flow in the corner region, but attached flow elsewhere in the diffuser. The results include flow visualization data corresponding to tuft and oil flow patterns observed on the diffuser walls and flow angle data taken in the immediate vicinity of the corner. Axial mean velocity distributions and local wall shear stress profiles are also presented. Analysis of the results provides new insight into the structure of separated, three-dimensional corner flows, wherein combined attached and detached flow conditions exist simultaneously at each streamwise location.

Experimental Study of the Flow in a Simulated Hard Disk Drive

2006 ◽  
Vol 128 (5) ◽  
pp. 1090-1100 ◽  
Author(s):  
Charlotte Barbier ◽  
Joseph A. C. Humphrey ◽  
Eric Maslen
Keyword(s):  
Hard Disk Drive ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Hard Disk ◽  
Disk Drive ◽  
Particle Image Velocimetry Technique ◽  
Mean Velocity ◽  
Local Flow ◽  
The Mean ◽  
Fundamental Value

Instantaneous circumferential and radial velocity components of the air flowing past a symmetrical pair of suspension/slider-units (SSUs) attached to an E-Block/arm were measured in a specially designed corotating disk apparatus simulating a hard disk drive (HDD) using the particle image velocimetry technique. The geometrical dimensions of the components in the apparatus test section were scaled up by a factor of two, approximately, relative to those of a nominal 312 inch HDD. Most of the measurements were obtained on the interdisk midplane for two angular orientations of the arm/SSUs: (a) One with the tip of the SSUs near the hub supporting the disks; (b) another with the tip of the SSUs near the rims of the disks. Data obtained for disk rotational speeds ranging from 250 to 3000rpm (corresponding to 1250 to 15,000rpm, approximately, in a 312 inch HDD) were post-processed to yield mean and rms values of the two velocity components and of the associated shear stress, the mean axial vorticity, and the turbulence intensity (based on the two velocity components). At the locations investigated near the arm/SSUs, and for disk rotational speeds larger than 1500rpm, the mean velocity components are found to be asymptotically independent of disk speed of rotation but their rms values appear to still be changing. At two locations 90 and 29deg, respectively, upstream of the arm/SSUs, the flow approaching this obstruction displays features that can be attributed to the three-dimensional wake generated by the obstruction. Also, between these two locations and depending on the angular orientation of the arm/SSUs, the effect of the obstruction is to induce a three-dimensional region of flow reversal adjacent to the hub. Notwithstanding, the characteristics of the flow immediately upstream and downstream of the arm/SSUs appear to be determined by local flow-structure interactions. Aside from their intrinsic fundamental value, the data serve to guide and test the development of turbulence models and numerical calculation procedures for predicting this complex class of confined rotating flows, and to inform the improved design of HDDs.

Three-Dimensional Fluid Flow Phenomena in the Blade End Wall Corner Region

1986 ◽  
Author(s):  
B. K. Hazarika ◽  
R. Raj ◽  
D. R. Boldman
Keyword(s):  
Flow Visualization ◽  
Relative Size ◽  
Three Dimensional ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Mean Velocity ◽  
Corner Region ◽  
Rate Of Spread ◽  
Flow Phenomena ◽  
End Wall

The three-dimensional flow in the blade end wall corner region was investigated. The techniques used in the investigation included flow visualization, static and total pressure measurements with conventional probes, and mean volocity profile measurements with a single sensor inclined hot-wire probe. Six critical axial stations along the blade chord were chosen for detailed measurements based on the flow visualization results. A large number of data points were obtained very close to the corner walls at each axial location including all the components of the mean velocity. Based on the measurements, three vortices were identified. A horseshoe vortex started near the leading edge. A corner eddy was formed between the horseshoe vortex and the corner. Another vortex was formed at the rear portion of the corner due to the secondary flow of the second kind. The relative size and the rate of spread of the vortices in the streamwise direction are discussed.

Correcting Inflow Measurements From Wind Turbines Using a Lifting-Surface Code

2000 ◽  
Vol 122 (4) ◽  
pp. 196-202 ◽  
Author(s):  
J. Whale ◽  
C. J. Fisichella ◽  
M. S. Selig
Keyword(s):  
Angle Of Attack ◽  
Three Dimensional ◽  
Correction Method ◽  
Local Flow ◽  
Flow Angle ◽  
Lifting Surface ◽  
Surface Code ◽  
Turbine Design ◽  
The Relationship ◽  
Blade Element

In order to provide accurate blade element data for wind turbine design codes, measured three-dimensional (3D) field data must be corrected in terms of the (sectional) angle of attack. A 3D Lifting-Surface Inflow Correction Method (LSIM) has been developed with the aid of a vortex-panel code in order to calculate the relationship between measured local flow angle and angle of attack. The results show the advantages of using the 3D LSIM correction over 2D correction methods, particularly at the inboard sections of the blade where the local flow is affected by post-stall effects and the influence of the blade root. [S0199-6231(00)00604-3]

Wall region of a relaxing three-dimensional incompressible turbulent boundary layer

1978 ◽  
Vol 85 (1) ◽  
pp. 33-56 ◽  
Author(s):  
K. S. Hebbar ◽  
W. L. Melnik
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Cross Flow ◽  
Wall Region ◽  
Mean Flow ◽  
Mean Velocity ◽  
Flow Angle ◽  
The Mean

An experimental investigation was conducted at selected locations in the wall region of a three-dimensional turbulent boundary layer relaxing in a nominally zero external pressure gradient behind a transverse hump (in the form of a 30° swept, 5 ft chord, wing-type model) faired into the side wall of a low-speed wind tunnel. The boundary layer (approximately 3·5 in. thick near the first survey station, where the length Reynolds number was 5·5 × 106) had a maximum cross-flow velocity ratio of 0·145 and a maximum cross-flow angle of 21·9° close to the wall. The hot-wire data indicated that the apparent dimensionless velocity profiles in the viscous sublayer are universal and that the wall influence on the hot wire is negligible beyond y+= 5. The existence of wall similarity in the relaxing flow field was confirmed in the form of a log law based on the resultant mean velocity and resultant friction velocity (obtained from the measured skin friction).The smallest collateral region extended from the point nearest to the wall (y+≈ 1) up to y+= 9·7, corresponding to a resultant mean velocity ratio (local to free-stream) of 0·187. The unusual feature of these profiles was the presence of a narrow region of slightly decreasing cross-flow angle (1° or less) that extended from the point of maximum cross-flow angle down to the outer limit of the collateral region. A sublayer analysis of the flow field using the measured local transverse pressure gradient slightly overestimated the decrease in cross-flow angle. It is concluded that, in the absence of these gradients, the skewing of the flow could have been much more pronounced practically down to the wall (limited only by the resolution of the sensor), implying a near-wallnon-collateralflow field consistent with the equations of motion in the neighbourhood of the wall.The streamwise relaxation of the mean flow field based on the decay of the cross-flow angle was much faster in the inner layer than in the outer layer. Over the stream-wise distance covered, the mean flow in the inner layer and the wall shear-stress vector relaxed to a two-dimensional state in approximately 10 boundary-layer thicknesses whereas the relaxation of the turbulence was slower and was not complete over the same distance.

A Study of Flow Downstream of a T-Junction and the Implications of its Effect (In Crude Oil Flow) on Water Droplet Size and Distribution

1993 ◽  
Vol 207 (2) ◽  
pp. 123-132
Author(s):  
C P Lenn ◽  
J Hemp ◽  
R C Baker ◽  
E R Hayes ◽  
A D Harper
Keyword(s):  
Crude Oil ◽  
Water Droplet ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Field Measurements ◽  
Maximum Size ◽  
Radial Component ◽  
Mean Velocity ◽  
Grab Sampling ◽  
Oil Flow

A laser Doppler anemometer (LDA) is used to measure velocity profiles and turbulence levels of water flow in the first few diameters downstream of a T-junction. The ‘vertical’ limb of the T-junction is half the diameter of the ‘horizontal’ limb, one end of which is blanked off. Flow passes from the smaller into the larger tube and LDA measurements of axial and tangential velocity components are conducted in the larger tube up to 3.75 diameters downstream of the T-junction at Reynolds numbers of 10.5 × 104 and 7.42 × 104. The pipe geometry is a commonly occurring configuration in crude oil pipelines and is of interest because of its possible ability to break up and mix water droplets to an extent sufficient for accurate grab sampling. LDA measurements of r.m.s. velocity fluctuations give information on the level of turbulent diffusivity and hence the maximum size of droplets that can be present in crude oil flow in the same geometry. A novel mathematical technique is used to interpolate between LDA measurements of mean velocity and to calculate the radial component of mean velocity. The three-dimensional velocity distributions thus formulated are used to predict water droplet concentration profiles downstream of the T-junction using the Segev approach—that is by solving numerically a differential equation for concentration of a contaminant under conditions of turbulent diffusion. Results are compared with field measurements in a similar geometry.

scholarly journals Detailed Measurements of the Flow Field in a Transonic Turbine Cascade

1991 ◽  
Author(s):  
E. Detemple-Laake
Keyword(s):  
Pressure Distribution ◽  
Three Dimensional ◽  
Side Wall ◽  
Turbine Rotor ◽  
Experimental Investigations ◽  
Flow Angle ◽  
Flow Models ◽  
Oil Flow ◽  
High Pressure Stage ◽  
Flow Effects

Systematic experimental investigations of the transonic flow through a plane cascade consisting of profiles designed for a highly loaded gas turbine rotor of a high pressure stage were performed. The experiments comprise side wall pressure distribution measurements in a blade passage and both profile pressure distribution and wake traverse measurements in various planes from midspan to the side wall. The parameters varied are the inlet flow angle and the downstream Mach number. Schlieren photopraphs and oil flow patterns on the blades and on the side wall are included. The experimental results are interpreted with respect to the existing flow models describing shock wave boundary layer interactions and secondary flow effects. The experimental data are compared with three-dimensional viscous numerical results.

scholarly journals Effects of coral colony morphology on turbulent flow dynamics

2019 ◽  
Author(s):  
Md Monir Hossain ◽  
Anne E. Staples
Keyword(s):  
Turbulent Flow ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
High Flow ◽  
Flow Dynamics ◽  
Immersed Boundary ◽  
Mean Velocity ◽  
Local Flow ◽  
The Mean ◽  
Mixing And Transport

AbstractLocal flow dynamics play a central role in physiological processes like respiration and nutrient uptake in coral reefs. Despite the importance of corals as hosts to a quarter of all marine life, and the pervasive threats currently facing corals, little is known about the detailed hydrodynamics of branching coral colonies. Here, in order to investigate the effects of the colony branch density and surface roughness on the local flow field, three-dimensional simulations were performed using immersed boundary, large-eddy simulations for four different colony geometries under low and high unidirectional oncoming flow conditions. The first two colonies were from the Pocillopora genus, one with a densely branched geometry, and one with a comparatively loosely branched geometry. The second pair of colony geometries were derived from a scan of a single Montipora capitata colony, one with the verrucae covering the surface intact, and one with the verrucae removed. We found that the mean velocity profiles in the densely branched colony changed substantially in the middle of the colony, becoming significantly reduced at middle heights where flow penetration was poor, while the mean velocity profiles in the loosely branched colony remained similar in character from the front to the back of the colony, with no middle-range velocity deficit appearing at the center of the colony. When comparing the turbulent flow statistics at the surface of the rough and smooth M. capitata colonies, we found higher Reynolds stress components for the smooth colony, indicating higher rates of mixing and transport compared to the rough colony, which must sacrifice mixing and transport efficiency in order to maintain its surface integrity in its natural high-flow environment. These results suggest that the densely branched, roughly patterned corals found in high flow areas may be more resistant not only to breakage, but also to flow penetration.

scholarly journals Analysis of Fan Stage Design Attributes for Boundary Layer Ingestion

2016 ◽  
Author(s):  
D. K. Hall ◽  
E. M. Greitzer ◽  
C. S. Tan
Keyword(s):  
Boundary Layer ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Surface Geometry ◽  
Flow Distortion ◽  
Local Flow ◽  
Stage Design ◽  
Flow Angle ◽  
Inlet Distortion ◽  
Design Attributes

This paper describes a new conceptual framework for three-dimensional turbomachinery flow analysis and its use to assess fan stage attributes for mitigating adverse effects of inlet distortion due to boundary layer ingestion (BLI). A non-axisymmetric throughflow method has been developed to describe the fan flow field with inlet distortion. In this the turbomachinery is modeled using momentum and energy source distributions that are determined as a function of local flow conditions and a specified blade camber surface geometry. Comparison with higher-fidelity computational and experimental results shows that the method captures the principal flow redistribution and distortion transfer effects associated with BLI. Distortion response is assessed for a range of (i) rotor spanwise work profiles, (ii) rotor-stator spacings, and (iii) non-axisymmetric stator geometries. For the parameters examined, changes in axisymmetric design result in trades between rotor and stator distortions, or between different radial sections of a given blade row with marginal overall gain. Of the approaches examined, non-axisymmetric stator exit flow angle distributions were found to provide the greatest reduction in rotor flow distortion and thus may offer the most potential for mitigating decreases in performance due to BLI inlet distortion.

EXPERIMENTAL INVESTIGATION OF FLOW RESPONSE TO STATIONARY DISTURBANCE IN ROTATING-DISK FLOW

2019 ◽  
Vol XVI (2) ◽  
pp. 13-22
Author(s):  
Muhammad Ehtisham Siddiqui
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Careful Analysis ◽  
Laboratory Frame ◽  
Transition To Turbulence ◽  
Turbulent Regime ◽  
Mean Velocity ◽  
Layer Flow

Three-dimensional boundary-layer flow is well known for its abrupt and sharp transition from laminar to turbulent regime. The presented study is a first attempt to achieve the target of delaying the natural transition to turbulence. The behaviour of two different shaped and sized stationary disturbances (in the laboratory frame) on the rotating-disk boundary layer flow is investigated. These disturbances are placed at dimensionless radial location (Rf = 340) which lies within the convectively unstable zone over a rotating-disk. Mean velocity profiles were measured using constant-temperature hot-wire anemometry. By careful analysis of experimental data, the instability of these disturbance wakes and its estimated orientation within the boundary-layer were investigated.

Disorganization of a hole tone feedback loop by an axisymmetric obstacle on a downstream end plate

2014 ◽  
Vol 757 ◽  
pp. 908-942 ◽  
Author(s):  
K. Matsuura ◽  
M. Nakano
Keyword(s):  
Nozzle Exit ◽  
Passive Control ◽  
Control Method ◽  
Three Dimensional ◽  
Acoustic Power ◽  
Shear Layers ◽  
Mean Velocity ◽  
End Plate ◽  
Air Jet ◽  
Practical Engineering

AbstractThis study investigates the suppression of the sound produced when a jet, issued from a circular nozzle or hole in a plate, goes through a similar hole in a second plate. The sound, known as a hole tone, is encountered in many practical engineering situations. The mean velocity of the air jet $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}u_0$ was $6\text {--}12\ \mathrm{m}\ {\mathrm{s}}^{-1}$. The nozzle and the end plate hole both had a diameter of 51 mm, and the impingement length $L_{im}$ between the nozzle and the end plate was 50–90 mm. We propose a novel passive control method of suppressing the tone with an axisymmetric obstacle on the end plate. We find that the effect of the obstacle is well described by the combination ($W/L_{im}$, $h$) where $W$ is the distance from the edge of the end plate hole to the inner wall of the obstacle, and $h$ is the obstacle height. The tone is suppressed when backflows from the obstacle affect the jet shear layers near the nozzle exit. We do a direct sound computation for a typical case where the tone is successfully suppressed. Axisymmetric uniformity observed in the uncontrolled case is broken almost completely in the controlled case. The destruction is maintained by the process in which three-dimensional vortices in the jet shear layers convect downstream, interact with the obstacle and recursively disturb the jet flow from the nozzle exit. While regions near the edge of the end plate hole are responsible for producing the sound in the controlled case as well as in the uncontrolled case, acoustic power in the controlled case is much lower than in the uncontrolled case because of the disorganized state.

Sign in / Sign up

Export Citation Format

Share Document