scholarly journals IDDES Evaluation of Oscillating Hydraulic Jumps

2018 ◽  
Vol 40 ◽  
pp. 05067 ◽  
Author(s):  
Vimaldoss Jesudhas ◽  
Frédéric Murzyn ◽  
Ram Balachandar
Keyword(s):  
Flow Field ◽  
Hydraulic Jump ◽  
Three Dimensional ◽  
Wall Jet ◽  
Hydraulic Jumps ◽  
Vortical Structures ◽  
Instantaneous Flow Field ◽  
Type Flow ◽  
Different Types ◽  
Flow Features

This paper presents the results of three-dimensional, unsteady, Improved Delayed Detached Eddy Simulations of an oscillating and a stable hydraulic jump at Froude numbers of 3.8 and 8.5, respectively. The different types of oscillations characterised in a hydraulic jump are analysed by evaluating the instantaneous flow field. The instability caused by the flapping wall-jet type flow in an oscillating jump is distinct compared to the jump-toe fluctuations caused by the spanwise vortices in the shear layer of a stable jump. These flow features are accurately captured by the simulations and are presented with pertinent discussions. The near-bed vortical structures in an oscillating jump is extracted and analysed using the λ2 criterion.

Aero-Thermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets: Part I—Flow Field Analysis

2008 ◽  
Author(s):  
Alessandro Armellini ◽  
Filippo Coletti ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Three Dimensional ◽  
Side Wall ◽  
Field Analysis ◽  
Trailing Edge ◽  
Present Contribution ◽  
Numerical Predictions ◽  
Flow Features ◽  
Rib Roughened

The present contribution addresses the aero-thermal experimental and computational study of a trapezoidal cross-section model simulating a trailing edge cooling cavity with one rib-roughened wall. The flow is fed through tilted slots on one side wall and exits through straight slots on the opposite side wall. The flow field aerodynamics is investigated in part I of the paper. The reference Reynolds number is defined at the entrance of the test section and set at 67500 for all the experiments. A qualitative flow model is deduced from surface-streamline flow visualizations. Two-dimensional Particle Image Velocimetry measurements are performed in several planes around mid-span of the channel and recombined to visualize and quantify three-dimensional flow features. The jets issued from the tilted slots are characterized and the jet-rib interaction is analyzed. Attention is drawn to the motion of the flow deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained from the finite volume, RANS solver CEDRE.

scholarly journals On the formation of the counter-rotating vortex pair in transverse jets

2001 ◽  
Vol 446 ◽  
pp. 347-373 ◽  
Author(s):  
L. CORTELEZZI ◽  
A. R. KARAGOZIAN
Keyword(s):  
Flow Field ◽  
Computational Study ◽  
Near Field ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Transverse Jets ◽  
Vortical Structures ◽  
Jet In Crossflow ◽  
Dynamical Generation ◽  
Counter Rotating Vortex Pair

Among the important physical phenomena associated with the jet in crossflow is the formation and evolution of vortical structures in the flow field, in particular the counter-rotating vortex pair (CVP) associated with the jet cross-section. The present computational study focuses on the mechanisms for the dynamical generation and evolution of these vortical structures. Transient numerical simulations of the flow field are performed using three-dimensional vortex elements. Vortex ring rollup, interactions, tilting, and folding are observed in the near field, consistent with the ideas described in the experimental work of Kelso, Lim & Perry (1996), for example. The time-averaged effect of these jet shear layer vortices, even over a single period of their evolution, is seen to result in initiation of the CVP. Further insight into the topology of the flow field, the formation of wake vortices, the entrainment of crossflow, and the effect of upstream boundary layer thickness is also provided in this study.

scholarly journals Transient Air-Water Flow and Air Demand following an Opening Outlet Gate

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
James Yang ◽  
Ting Liu ◽  
Wenhong Dai ◽  
Penghua Teng
Keyword(s):  
Water Flow ◽  
Hydraulic Jump ◽  
Three Dimensional ◽  
Cfd Simulations ◽  
Wire Ropes ◽  
Air Supply ◽  
Flow Features ◽  
Demand Rate ◽  
Air Pockets ◽  
Bottom Outlets

In Sweden, the dam-safety guidelines call for an overhaul of many existing bottom outlets. During the opening of an outlet gate, understanding the transient air-water flow is essential for its safe operation, especially under submerged tailwater conditions. Three-dimensional CFD simulations are undertaken to examine air-water flow behaviors at both free and submerged outflows. The gate, hoisted by wire ropes and powered by AC, opens at a constant speed. A mesh is adapted to follow the gate movement. At the free outflow, the CFD simulations and model tests agree well in terms of outlet discharge capacity. Larger air vents lead to more air supply; the increment becomes, however, limited if the vent area is larger than 10 m2. At the submerged outflow, a hydraulic jump builds up in the conduit when the gate reaches approximately 45% of its full opening. The discharge is affected by the tailwater and slightly by the flow with the hydraulic jump. The flow features strong turbulent mixing of air and water, with build-up and break-up of air pockets and collisions of defragmented water bodies. The air demand rate is several times as much as required by steady-state hydraulic jump with free surface.

Three-dimensional study of spatial submerged hydraulic jump

2007 ◽  
Vol 34 (9) ◽  
pp. 1140-1148 ◽  
Author(s):  
H K Zare ◽  
R E Baddour
Keyword(s):  
Velocity Field ◽  
Hydraulic Jump ◽  
Three Dimensional ◽  
Head Loss ◽  
Acoustic Doppler Velocimeter ◽  
Hydraulic Jumps ◽  
Orthogonal Components ◽  
Sequent Depth ◽  
Channel Bottom ◽  
Submerged Hydraulic Jump

A three-dimensional (3D) study of spatial submerged hydraulic jumps (SSHJs) was carried out using a physical model for Froude numbers Fr1 = 2.00 and 3.75 and width ratios α = 0.20 and 0.33. Three orthogonal components of the velocity field were obtained with an acoustic Doppler velocimeter (ADV). The 3D velocity field has indicated that the jump consisted of a central jet-like flow, close to the channel bottom, surrounded by vertical and horizontal circulations (rollers). The circulation was predominantly in vertical planes in the channel central region of the flow and in horizontal planes close to the walls. Vertical and horizontal profiles of stream-wise velocity characterized the 3D roller with two length scales, Lrv and Lrh. The strength of the roller was stronger close to the walls than at the centreline of the jump. Sequent depth and energy head loss for submerged symmetric hydraulic jumps are discussed in terms of the submergence ratio S = y3/y2.Key words: hydraulic jump, spatial, submerged, roller length, sequent depth, energy dissipation.

Three-dimensional flow within shallow, narrow cavities

2013 ◽  
Vol 735 ◽  
pp. 587-612 ◽  
Author(s):  
Sarah D. Crook ◽  
Timothy C. W. Lau ◽  
Richard M. Kelso
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Particle Image Velocimetry Data ◽  
Cavity Flow ◽  
Dimensional Structure ◽  
Back Surface ◽  
Flow Topology ◽  
Open Type ◽  
Flow Features ◽  
Cavity Opening

AbstractThe three-dimensional structure of incompressible flow in a narrow, open rectangular cavity in a flat plate was investigated with a focus on the flow topology of the time-averaged flow. The ratio of cavity length (in the direction of the flow) to width to depth was $l{: }w{: }d= 6{: }2{: }1$. Experimental surface pressure data (in air) and particle image velocimetry data (in water) were obtained at low speed with free-stream Reynolds numbers of ${\mathit{Re}}_{l} = 3. 4\times 1{0}^{5} $ in air and ${\mathit{Re}}_{l} = 4. 3\times 1{0}^{4} $ in water. The experimental results show that the three-dimensional cavity flow is of the ‘open’ type, with an overall flow structure that bears some similarity to the structure observed in nominally two-dimensional cavities, but with a high degree of three-dimensionality both in the flow near the walls and in the unsteady behaviour. The defining features of an open-type cavity flow include a shear layer that traverses the entire cavity opening ultimately impinging on the back surface of the cavity, and a large recirculation zone within the cavity itself. Other flow features that have been identified in the current study include two vortices at the back of the cavity, of which one is barely visible, a weak vortex at the front of the cavity, and a pair of counter-rotating streamwise vortices along the sides of the cavity near the cavity opening. These vortices are generally symmetric about the cavity centre-plane. However, the discovery of a single tornado vortex, located near the cavity centreline at the front of the cavity, indicated that the flow within the cavity is asymmetric. It is postulated that the observed asymmetry in the time-averaged flow field is due to the asymmetry in the instantaneous flow field, which switches between two extremes at large time scales.

Turbulence Measurements in the Corner Wall Jet

2014 ◽  
Author(s):  
Barrett Poole ◽  
Joseph W. Hall
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Wall Jet ◽  
Hot Wire ◽  
Turbulence Measurements ◽  
Vertical Growth ◽  
The Mean ◽  
Turbulent Flow Field

The corner wall jet is similar to the standard three-dimensional wall jet with the exception that one half of the surface has been rotated counter-clockwise by 90 degrees. The corner wall jet investigated here is formed using a long round pipe with a Reynolds number of 159,000. Contours of the mean and turbulent flow field were measured using hot-wire anemometry. The results indicate that the ratio of lateral to vertical growth in the corner wall jet is approximately half of that in a standard turbulent three-dimensional wall jet.

Laminar Fluid Flow around Two Wall-Mounted Cubes of Arbitrary Configuration

2010 ◽  
Vol 224 (11) ◽  
pp. 2396-2407 ◽  
Author(s):  
M Eslami ◽  
M M Tavakol ◽  
E Goshtasbirad
Keyword(s):  
Fluid Flow ◽  
Flow Field ◽  
Free Stream ◽  
Three Dimensional ◽  
Bluff Bodies ◽  
Vortical Structures ◽  
Laminar Fluid Flow ◽  
Pressure Distributions ◽  
Arbitrary Configuration ◽  
Computational Fluid Dynamics Cfd

The problem of flow field around multiple bluff bodies mounted on a surface is of great significance in different fields of engineering. In this study, a computational fluid dynamics (CFD) code is developed to calculate three-dimensional (3D) steady state laminar fluid flow around two cuboids of arbitrary size and configuration mounted on a surface in free stream conditions. This study presents the results for two cubes of the same size mounted on a surface in both inline and staggered arrangements. Streamlines are plotted for various combinations of the distance between the two cubes and Reynolds number. Moreover, the effects of different parameters on vortical structures, separation, and reattachment points are discussed. Also, velocity and pressure distributions are plotted in the wake region behind the two cubes. It is clearly shown that how the presence of the second cube changes the flow field and the vortical structures in comparison with the case of a single cube.

Investigations on Energy Shares and Flow Structures of the Mixing Flow Using 3D-POD Analyses

2019 ◽  
Author(s):  
Daekyeong Kong ◽  
Gyeongrae Cho ◽  
Myoung-Jin Kim ◽  
Deog Hee Doh ◽  
Sangmo Kang ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Flow Structures ◽  
Optical Encoder ◽  
Energy Distributions ◽  
Three Dimensional Flow ◽  
Mixing Properties ◽  
Vortical Structures ◽  
Flow Features ◽  
Proper Orthogonal

Abstract The objective of this report is investigate the influences of the mixing state to the productions of the vaterite crystal of CaCO3. In order to quantify the three-dimensional flow structures and their physical contribution to the mixing properties, a stereoscopic PIV (SPIV) has been adopted. The SPIV systems consists of two high speed cameras and an optical encoder which is used for trigging the SPIV system to capture the instantaneous flow images. A continuous laser (550nm) has been used. For mixing, an agitator having four blades has been used. The mixing tank has been filled with water up to 85% level of the tank height. The agitator has been rotated with 200rpm, 250rpm and 300rpm, and the 3D flow structures have been captured by the constructed SPIV system. Using measured instantaneous 3D vectors, POD (proper orthogonal decomposition) analyses has been adopted to investigate the energy distributions of the major vortical structures, and to evaluate the flow features regarding on the production of the vaterite crystal of CaCO3.

PIV Measurements of Recirculation Patterns in a Stirred Tank

2001 ◽  
Author(s):  
Khaled J. Hammad ◽  
George Papadopoulos
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Vertical Axis ◽  
Transitional Flow ◽  
Piv Measurements ◽  
Vortical Structures ◽  
Blade Passage ◽  
Flow Field Characteristics

Abstract Phase-resolved PIV measurements were performed to reveal the detailed flow features within a triple impeller stirredtank. Two tests were performed: low and high rotational speeds, 175 and 575 RPM, respectively. The tests used an optically transparent mixing vessel to measure the 2D flow field characteristics along a vertical plane passing through the tank center. The measurements disclosed interesting in-plane vortical behavior that when measured at two angular positions with respect to the blade passage further indicated the three-dimensional flow behavior. For the low RPM case, a laminar flow nature was apparent, whereby vortical toroidal structures spanned around the stirrer vertical axis. Six such structures were dominant. For the high RPM case and for θ = 0° six dominant vortical structures were apparent. Their r-z plane location and size were different from that for the low RPM case. With blade passage four of these vortical structures appeared to merge into two, suggesting that constant toroidal vortical structures spanning around the stirrer axis were absent from the high RPM case. A switch between six distinct and four distinct in-plane vortical structures as the blades pass through the measurement plane further suggested a transitional flow field at 575 RPM.

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