Obstacle drag in stratified flow

1990 ◽  
Vol 429 (1876) ◽  
pp. 119-140 ◽  
Keyword(s):  
Experimental Study ◽  
Linear Density ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Force Balance ◽  
Video Recordings ◽  
Lee Waves ◽  
Time Variations ◽  
Obstacle Height ◽  
Stable Linear

This paper describes an experimental study of the drag of two- and three-dimensional bluff obstacles of various cross-stream shapes when towed through a fluid having a stable, linear density gradient with Brunt-Vaisala frequency, N . Drag measurements were made directly using a force balance, and effects of obstacle blockage ( h / D , where h and D are the obstacle height and the fluid depth, respectively) and Reynolds number were effectively eliminated. It is shown that even in cases where the downstream lee waves and propagating columnar waves are of large amplitude, the variation of drag with the parameter K ( = ND /π U ) is qualitatively close to that implied by linear theories, with drag minima existing at integral values of K . Under certain conditions large, steady, periodic variations in drag occur. Simultaneous drag measurements and video recordings of the wakes show that this unsteadiness is linked directly with time-variations in the lee and columnar wave amplitudes. It is argued that there are, therefore, situations where the inviscid flow is always unsteady even for large times; the consequent implications for atmospheric motions are discussed.

Simulation and Experimental Study on the Impact of Breadth of Back Blade on Axial Force Balance

2011 ◽  
Vol 130-134 ◽  
pp. 1568-1572
Author(s):  
Hui Wang ◽  
Jie Gang Mu ◽  
Miao Yin Su ◽  
Shui Hua Zheng ◽  
Jin Jing Zhao ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Experimental Study ◽  
Axial Force ◽  
Three Dimensional ◽  
Force Balance ◽  
Simulation And Experiment ◽  
Simulation Results ◽  
The Impact ◽  
The Relationship

The paper studies the relationship between axial force and breadth of back blade by numerical simulation and experiment. On the basis of the RNG k-ε turbulence model and technology of compact local grids and regional computing, three dimensional numerical simulations to 100HZ165-250 centrifugal pump with various breadths were carried out. Through comparing and analyzing of the flow field, it can be seen that the axial force reduces with the increase of the back blade breadth. After that, the simulation results were verified by the experimental data got from different test devices, and it shows that the conclusions are reliable.

On the structure of inertial waves produced by an obstacle in a deep, rotating container

1979 ◽  
Vol 91 (3) ◽  
pp. 415-432 ◽  
Author(s):  
K. Stewartson ◽  
H. K. Cheng
Keyword(s):  
Asymptotic Theory ◽  
Rotation Axis ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
The Body ◽  
Transverse Motion ◽  
Rossby Number ◽  
Lee Waves ◽  
Inertial Wave ◽  
Thin Obstacle

The inviscid flow above an obstacle in slow transverse motion inside a rotating vessel is analysed to study the influence of the container depth on the basic steady flow structure. An asymptotic theory is presented for an arbitrarily small Rossby number Ro = U0/2Ωl under a fixed H = hRo/l (where Ω is the angular velocity of the container, U0 the obstacle velocity relative to the vessel, h the depth of the container, and l a body length measured transversely to the rotation axis). The equations when linearized for a thin obstacle or shallow topography take on the form of the inertial-wave equation; their solutions for non-vanishing H are obtained for obstacles of three-dimensional as well as ridge-like two-dimensional shapes. In all cases analysed, the solution possesses a bimodal structure, of which one part is column-like with a vorticity proportional to the body elevation (or ground topography). The other part is confined mainly to a region enclosing the body, extending a distance O(H½) upstream of the obstacle and behind a wedge-shaped caustic front at large distances; its contribution consists of lee waves similar to that discussed by Cheng (1977) for an infinite depth. The field associated with the lee waves is then biased on the downstream side, but there is little indication of any tendency to tilting in the sense of Hide, Ibbetson & Lighthill (1968).

Visualizing Methods of Multi-criteria Alternatives for Pairwise Comparison Procedure

2020 ◽  
Author(s):  
Alena Zaharova ◽  
Dmitriy Aleksandrovich Korostelev
Keyword(s):  
Decision Making ◽  
Experimental Study ◽  
Probability Distribution ◽  
Three Dimensional ◽  
Pairwise Comparison ◽  
Inviscid Flow ◽  
Two Dimensional ◽  
Combined Method ◽  
Visualization Tools ◽  
Flow Around A Cone

The article deals with the problem of choosing a preferred alternative in a pairwise comparison procedure. The difficulties of applying this procedure in a case of using alternatives with a large number of criteria are noted. It is proposed to supplement the procedure of expert pairwise comparison with visualization tools of multi-criteria alternatives. The paper considers several visualization methods for multi-criteria alternatives for pairwise comparison procedures: histograms, two-dimensional graphs, three-dimensional surfaces, probability distribution diagrams, visualization based on modifications of radar and radial diagrams, as well as combined methods. It described an experimental study of the application of the considered method for the task of determining the preferred alternative by the example of choosing one of two OpenFoam solvers (rhoCentralFoam and pisaCentralFoam), with the help of which estimates of the accuracy of calculating the inviscid flow around a cone were obtained. Each solver is characterized by 288 criteria. It is shown that the use of some of the methods considered does not make it possible for the expert to make a choice. In this case, a good result was obtained using methods for constructing three-dimensional surfaces, probability distribution diagrams, as well as using the combined method based on modified radar diagrams. It is concluded that the rhoCentralFoam solver is more preferable if there are no additional criteria for ranking the criteria. The possibility of using the combined method in combination with the ranking procedure of criteria (or their groups) during decision-making is also noted.

Optimization of the Three-Dimensional Flow Path in the Scroll-Nozzle System of a Radial Inflow Turbine

1984 ◽  
Vol 106 (2) ◽  
pp. 511-515 ◽  
Author(s):  
E. A. Baskharone
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Three Dimensional Flow ◽  
Multiply Connected ◽  
Dimensional Flow ◽  
Nozzle Configuration ◽  
Flow Domain ◽  
Radial Inflow Turbine ◽  
Compressibility Effects

A three-dimensional inviscid flow analysis in the combined scroll-nozzle system of a radial inflow turbine is presented. The coupling of the two turbine components leads to a geometrically complicated, multiply-connected flow domain. Nevertheless, this coupling accounts for the mutual effects of both elements on the three-dimensional flow pattern throughout the entire system. Compressibility effects are treated for an accurate prediction of the nozzle performance. Different geometrical configurations of both the scroll passage and the nozzle region are investigated for optimum performance. The results corresponding to a sample scroll-nozzle configuration are verified by experimental measurements.

Three-dimensional inviscid flow analysis of turbofan forced mixers

1985 ◽  
Author(s):  
T. BARBER ◽  
G. MULLER ◽  
S. RAMSAY ◽  
E. MURMAN
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Inviscid Flow
Sign in / Sign up

Export Citation Format

Share Document