scholarly journals Experimental Observations on the Flow Past a Plano-Convex Hydrofoil

1966 ◽  
Vol 88 (1) ◽  
pp. 273-282 ◽  
Author(s):  
R. B. Wade ◽  
A. J. Acosta
Keyword(s):  
Cavity Length ◽  
Angle Of Attack ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Average Force ◽  
Periodic Oscillations ◽  
Peak Magnitude ◽  
Flow Past ◽  
Reduced Frequency ◽  
Partial Cavitation

Some new measurements and observations on the noncavitating and cavitating flow past a plano-convex hydrofoil are presented. Under some conditions of partial cavitation, strong, periodic oscillations both in the cavity length and forces exerted on the hydrofoil are observed. The reduced frequency of oscillation depends upon the cavitation number and angle of attack; it also depends somewhat on tunnel speed for the lower angles of attack but becomes substantially independent of speed for the highest angle. The peak-to-peak magnitude of the force oscillation can amount to about 20 percent of the average force.

Cavitation Characteristics of S-Blade Used in Fully Reversible Pump-Turbine

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
T. M. Premkumar ◽  
Pankaj Kumar ◽  
Dhiman Chatterjee
Keyword(s):  
Angle Of Attack ◽  
Visual Observation ◽  
Cavitating Flow ◽  
Hydrodynamic Performance ◽  
Cloud Cavitation ◽  
Cavitation Inception ◽  
Cavitation Effect ◽  
Flow Past ◽  
Turbulence Transition ◽  
Numerical Characterization

S-shaped blade profiles with double camber find use in fully reversible turbomachines that can extract power from tides. Though noncavitating characteristics of S-blades were determined in the past, yet characterizing cavitating flow was not carried out. This work, which is the first step in this direction, uses a two-pronged approach of experimental and numerical characterization of cavitating flow past these hydrofoils. Experimental results indicate that as the angle of attack increases in either positive or negative directions, cavitation inception number increases. Minimum cavitation effect is observed at 2 deg, which is zero lift angle of attack. For higher angles of attack (±6deg, ±4deg) and moderate or low cavitation number (σ/σi≤0.3), unsteady cloud cavitation was characterized through visual observation and from pressure fluctuation data. It was observed that for unsteady cavity shedding to take place is the length and thickness of the cavity should be more than 50% and 10% of the chord length, respectively. Predicting flow past this geometry is difficult and the problem may be compounded in many applications because of laminar-to-turbulence transition as well as due to the presence of cavitation. Present simulations indicate that the k-kL-ω transition model may be useful in predicting hydrodynamic performance of this type of geometry and for the range of Reynolds number considered in this paper. Hydrodynamic performance under cavitation indicates that pumping mode is more adversely affected by cavitation and, hence, a fully reversible turbomachine may not perform equally well in turbine and pump modes as expected from noncavitating results.

An Extension of the Woods Theory for Unsteady Cavity Flows

1967 ◽  
Vol 89 (4) ◽  
pp. 789-806 ◽  
Author(s):  
H. R. Kelly
Keyword(s):  
Angle Of Attack ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Cavity Flows ◽  
Two Dimensional ◽  
Linearized Problem

One of the most useful theories for the design of hydrofoils for use in cavitating flow has been that of L. C. Woods. He solved the linearized problem for a two-dimensional hydrofoil in Helmholtz flow, at zero angle of attack, and tabulated the results. His theory is here extended to include nonzero cavitation number and nonzero angle of attack. The results are tabulated and some are compared with the original Woods theory.

Rarefied gas flow past a flat plate at zero angle of attack

2020 ◽  
Vol 32 (8) ◽  
pp. 087108
Author(s):  
A. A. Abramov ◽  
A. V. Butkovskii ◽  
O. G. Buzykin
Keyword(s):  
Flat Plate ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Angle Of Attack ◽  
Rarefied Gas Flow ◽  
Flow Past

Assessment of Tandem Venturi on Enhancement of Cavitational Chemical Reaction

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Hoseyn Sayyaadi
Keyword(s):  
Chemical Reaction ◽  
Oxidation Process ◽  
Flow Characteristics ◽  
Chemical Oxidation ◽  
Cavitation Number ◽  
Cavitating Flow ◽  
Hydrodynamic Cavitation ◽  
Operating Pressure ◽  
Local Pressures ◽  
Second Category

The collapsing phenomenon of cavitation bubbles generates extremely high local pressures and temperatures that can be utilized for the chemical oxidation process. This process is carried out in cavitation reactors. A Venturi tube is one of the most common forms of hydrodynamic cavitation reactors, which is suitable for industrial scale applications. In this work, the hydraulic performance and efficiency in chemical reaction of a new form of hydrodynamic cavitation reactors, which is called “tandem Venturi,” were studied and compared with the conventional type of the single Venturi. The tandem Venturi is used for enhancement of the chemical reaction of hydrodynamic cavitating flow. The reaction enhancement is useful especially for the reaction of aqueous solutions not containing volatile organic compounds (VOCs). The operating pressure, inlet pressure, flow rate, and consequently the cavitation number were controlled and systematically varied for both single and tandem Venturis. Moreover, a specified amount of H2O2 was injected into the flow as required. The effects of operating pressure and the cavitation number on cavitating flow characteristics for single and tandem Venturis were experimentally observed and the results were compared. In addition, the performance of the tandem-Venturi reactor for degradation of non-VOC contaminants (2-chlorophenol) was studied. Its performance was compared with the performance of a conventional Venturi reactor. Two different categories were conducted for the experiments. In the first category, the effect of the net cavitating flow on degradation of non-VOC for the single and tandem Venturis was compared. In the second category, the effect of H2O2 injection into the cavitating flow on degradation of non-VOC (“cavitation-oxidation” process) was studied. The performance of the single and tandem Venturis for the cavitation-oxidation process was compared. Further investigation was performed to assess the advantage of utilizing the tandem Venturi from the viewpoint of efficiency of the oxidation process. The results of the energy efficiency were compared with the corresponding efficiency of the single Venturi. Finally, the relationship between the main parameters of cavitation reaction flow with the chemical performance was discussed.

scholarly journals Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Kengo Kikuta ◽  
Noriyuki Shimiya ◽  
Tomoyuki Hashimoto ◽  
Mitsuru Shimagaki ◽  
Hideaki Nanri ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Pressure Rise ◽  
Cavitation Number ◽  
Design Parameters ◽  
Trailing Edge ◽  
Thermodynamic Effect ◽  
Blade Tip

Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

Accelerated flow past a symmetric aerofoil: experiments and computations

2007 ◽  
Vol 591 ◽  
pp. 255-288 ◽  
Author(s):  
T. K. SENGUPTA ◽  
T. T. LIM ◽  
SHARANAPPA V. SAJJAN ◽  
S. GANESH ◽  
J. SORIA
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Angle Of Attack ◽  
Stream Velocity ◽  
Published Data ◽  
Navier Stokes Equation ◽  
Moment Coefficient ◽  
Flow Past ◽  
Naca 0015 ◽  
Accelerated Flow

Accelerated flow past a NACA 0015 aerofoil is investigated experimentally and computationally for Reynolds number Re = 7968 at an angle of attack α = 30°. Experiments are conducted in a specially designed piston-driven water tunnel capable of producing free-stream velocity with different ramp-type accelerations, and the DPIV technique is used to measure the resulting flow field past the aerofoil. Computations are also performed for other published data on flow past an NACA 0015 aerofoil in the range 5200 ≤ Re ≤ 35000, at different angles of attack. One of the motivations is to see if the salient features of the flow captured experimentally can be reproduced numerically. These computations to solve the incompressible Navier–Stokes equation are performed using high-accuracy compact schemes. Load and moment coefficient variations with time are obtained by solving the Poisson equation for the total pressure in the flow field. Results have also been analysed using the proper orthogonal decomposition technique to understand better the evolving vorticity field and its dependence on Reynolds number and angle of attack. An energy-based stability analysis is performed to understand unsteady flow separation.

Cavitating Flow Past a Large Aspect-Ratio Hydrofoil

1961 ◽  
Vol 5 (01) ◽  
pp. 1-8
Author(s):  
E. Cumberbatch
Keyword(s):  
Aspect Ratio ◽  
Cavity Flow ◽  
Horseshoe Vortex ◽  
Cavitating Flow ◽  
Large Aspect Ratio ◽  
Central Section ◽  
Tip Vortices ◽  
Vortex Model ◽  
Flow Past ◽  
Good Comparison

Tip effects on the cavitating flow past a large aspect-ratio lifting hydrofoil are considered. The tip vortices arising from the flow leakage around the tip from the lower to the upper side of the hydrofoil are assumed to cavitate. The flow over the central section of the hydrofoil is taken as two-dimensional cavity flow and hence there is a wide planar cavity there. The separate cavity regions are taken not to coalesce. The flow is represented by a simple horseshoe-vortex model and descriptions of the flow over the central section, near the tip and well downstream, are derived and appropriately matched. The lift on the hydrofoil is then calculated, taking the downwash into account. The lift is seen to be reduced by the tip effects, and shows good comparison with experimental results.

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