scholarly journals Cavitation upon low-speed solid–liquid impact

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nathan B. Speirs ◽  
Kenneth R. Langley ◽  
Zhao Pan ◽  
Tadd T. Truscott ◽  
Sigurdur T. Thoroddsen
Keyword(s):  
High Pressures ◽  
Cavitation Number ◽  
Bottom Surface ◽  
Pressure Waves ◽  
Local Pressure ◽  
Classical Physics ◽  
Low Speed ◽  
Liquid Impact ◽  
Large Pressure ◽  
Solid Liquid

AbstractWhen a solid object impacts on the surface of a liquid, extremely high pressure develops at the site of contact. Von Karman’s study of this classical physics problem showed that the pressure on the bottom surface of the impacting body approaches infinity for flat impacts. Yet, in contrast to the high pressures found from experience and in previous studies, we show that a flat-bottomed cylinder impacting a pool of liquid can decrease the local pressure sufficiently to cavitate the liquid. Cavitation occurs because the liquid is slightly compressible and impact creates large pressure waves that reflect from the free surface to form negative pressure regions. We find that an impact velocity as low as ~3 m/s suffices to cavitate the liquid and propose a new cavitation number to predict cavitation onset in low-speed solid-liquid impact-scenarios. These findings imply that localized cavitation could occur in impacts such as boat slamming, cliff jumping, and ocean landing of spacecraft.

Aerodynamics of Cooling Jets Introduced in the Secondary Flow of a Low-Speed Turbine Cascade

1990 ◽  
Vol 112 (3) ◽  
pp. 539-546 ◽  
Author(s):  
F. Bario ◽  
F. Leboeuf ◽  
A. Onvani ◽  
A. Seddini
Keyword(s):  
Secondary Flow ◽  
Side Wall ◽  
Velocity Fields ◽  
Measuring Apparatus ◽  
Flow Ratio ◽  
Turbine Cascade ◽  
Hot Wire ◽  
Local Pressure ◽  
Low Speed ◽  
Jet Behavior

The aerodynamic behavior of cold discrete jets in a cold secondary flow is investigated. Configurations including single jets and rows of jets are studied. These jets are introduced through the side wall of a low-speed nozzle turbine cascade. The experimental setup and the jet behavior are fully described. The effects of location with respect to the blades, mass flow ratio, yaw, and incidence angles on the aerodynamics of single jets are investigated. The influence of neighboring jets is detailed in the case of multiple jet configurations. The interaction with the secondary flow is presented. The local pressure and velocity fields, trajectories, and visualizations are discussed. The measuring apparatus includes a five-hole probe and a hot wire for intermittency measurements.

scholarly journals Differential Sea-Ice Drift. II. Comparison of Mesoscale Strain Measurements to Linear Drift Theory Predictions

1974 ◽  
Vol 13 (69) ◽  
pp. 457-471 ◽  
Author(s):  
W. D. Hibler
Keyword(s):  
High Pressures ◽  
Constitutive Law ◽  
Elastic Behavior ◽  
Local Pressure ◽  
Strain Measurements ◽  
Linear Drift ◽  
Special Cases ◽  
Drift Theory ◽  
Sea Ice Drift ◽  
Frequency Behavior

A comparison of mesoscale strain measurements with the atmospheric pressure field and the wind velocity field indicate that the ice divergence rate and vorticity follow the local pressure and wind divergence with significant correlation. For low atmospheric pressures and converging winds the divergence rate was found to be negative with the vorticity being counter-clockwise. The inverse behavior was observed for high pressures and diverging winds. This behavior was shown to agree with predictions based upon the infinite boundary solution of a linearized drift theory in the absence of gradient current effects and using the constitutive law proposed by Glen (1970) for pack ice. The best least-squares values of the constitutive law parametersηandζwere found to be ≈ 1012kg/s. Using typical divergence rates these values yield compressive stresses of the magnitude of 105N/m which are similar to values suggested by the Parmerter and Coon (1972) ridge model. In general, the infinite boundary solution of the linear drift equation indicates that in a low-pressure region that is reasonably localized in space, the ice would be expected to converge for high compactness (winter) and diverge for low compactness (summer).Calculations were also carried out using a more general linear visco-elastic constitutive law that includes memory effects and which includes a generalized Hooke’s law as well as the Glen law as special cases. A best fit of this more general calculation with strain measurements indicates overall a better agreement with viscous behavior than with elastic behavior, with the frequency behavior of the estimated “viscosities” similar to the Glen law behavior at temporal frequencies less than ≈ 0.01 h−1.

Design of a centralized regional water distribution system: a case study in the County of Paintearth No. 18, Alberta, Canada

2012 ◽  
Vol 39 (7) ◽  
pp. 801-811 ◽  
Author(s):  
Mathew Langford ◽  
Jean-Luc Daviau ◽  
David Z. Zhu
Keyword(s):  
Rural Communities ◽  
Rural Areas ◽  
Distribution System ◽  
Water Distribution ◽  
High Pressures ◽  
Population Distribution ◽  
Pressure Control ◽  
Local Pressure ◽  
Head Losses ◽  
Sparse Population

Water supply to rural communities has historically been difficult. The sparse population distribution results in large infrastructure cost per capita compared to larger urban municipalities. The challenge is to deliver this water efficiently and minimize the corresponding increase in wastewater. Urban water systems supply both fire flow and drinking water at high pressures in large pipes. One solution for rural areas is supplying only potable water using small pipes that are supplied in long spools and that can be ploughed-in, a novel method of direct-bury. This water is delivered to private cisterns at low pressure, extending the range of the system for the same input energy level. Pressure control valves are used to keep pressure positive at high points to safeguard water quality. Modelling is particularly important in rural systems, where extensive pipeline distances and elevation difference result in significant head losses and areas of high local pressure.

scholarly journals Improvement of Aerodynamic Performance of Cambered Airfoils Using Leading-Edge Slots

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Bottom Surface ◽  
Original Design ◽  
Local Pressure ◽  
Maximum Increase ◽  
Average Improvement ◽  
Length Width ◽  
Inlet Angle

Feasibility of increasing lift and decreasing drag by drilling narrow span-wide channels near the leading edge of NACA 4412 airfoils is investigated. It is proposed to drill two-segment slots that allow some of the incoming air to flow through them and then exit from the bottom surface of the airfoil. Such slots can result in an increased local pressure and thereby higher lift. Length, width, inlet angle, and exit angle of slots are varied to determine optimum configurations. Aerodynamic performance at different angles of attack (AoAs) and the chord-based Reynolds number of 1.6 × 106 is investigated. It is concluded that longer and narrower slots with exit streams more aligned with the air flowing below the airfoil can result in a higher lift. Also, in order to keep the slotted airfoils beneficial for AoAs greater than zero, it is proposed to (a) slightly lower the slot position with respect to the original design and (b) tilt up the first-leg by a few degrees. For the best design case considered, an average improvement of 8% is observed for lift coefficient over the entire range of AoA (with the maximum increase of 15% for AoA = 0), without any significant drag penalty.

Modelling the Influence of Wetting Properties on the Solid Liquid Impact

2008 ◽  
Author(s):  
Minh Do-Quang ◽  
Gustav Amberg
Keyword(s):  
Liquid Surface ◽  
Solid Sphere ◽  
Navier Stokes ◽  
Dynamic Wetting ◽  
Wetting Properties ◽  
Liquid Impact ◽  
Free Air ◽  
Small Change ◽  
Solid Liquid ◽  
The Impact

The impact of a solid object on a free liquid surface is quite complex. This problem has challenged researchers for centuries and remains of interest today. Recently Duez et al. [1] published experimental results on the splash when a solid sphere enters a liquid. Surprisingly, a small change in the surface chemistry of the object can turn a big splash into an inconspicuous disappearance and vice versa. We study this problem by solving the Navier-Stokes together with the Cahn-Hilliard equations, [2, 3], which allows us to simulate the motion of a free air-water surface in detail, in the presence of surface tension and dynamic wetting. Quantitative computational modeling of dynamic wetting is difficult in itself, but here the use of this tool allows us to study in detail how the wetting properties determine whether a splash appears or not. Our simulated results are compared with the experiments of Duez et al.

scholarly journals Water entry of spheres with various contact angles

2019 ◽  
Vol 862 ◽  
Author(s):  
Nathan B. Speirs ◽  
Mohammad M. Mansoor ◽  
Jesse Belden ◽  
Tadd T. Truscott
Keyword(s):  
Contact Angle ◽  
Weber Number ◽  
Bond Number ◽  
Water Entry ◽  
Contact Angles ◽  
Cavity Formation ◽  
Liquid Impact ◽  
Critical Impact Velocity ◽  
Solid Liquid ◽  
Rough Sphere

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid–liquid contact angle; Duez et al. (Nat. Phys., vol. 3 (3), 2007, pp. 180–183). Using a rough sphere with a contact angle of $120^{\circ }$ , Aristoff & Bush (J. Fluid Mech., vol. 619, 2009, pp. 45–78) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasistatic, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: (1) cavity shape also depends on the contact angle; (2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we use alternate scales in defining the Bond, Weber and Froude numbers to predict the cavity shapes and scale pinch-off times for various impacting bodies (e.g., spheres, multidroplet streams and jets) on the same plots, merging the often separated studies of solid–liquid and liquid–liquid impact in the literature.

scholarly journals The Virial Effect—Applications for SF6 and CH4 Thermal Plasmas

2019 ◽  
Vol 9 (5) ◽  
pp. 929
Author(s):  
Andriniaina Harry Solo ◽  
Pierre Freton ◽  
Jean-Jacques Gonzalez
Keyword(s):  
High Pressure ◽  
Pressure Range ◽  
High Pressures ◽  
Local Thermodynamic Equilibrium ◽  
Good Alternative ◽  
Mass Action ◽  
Lennard Jones ◽  
Engineering Data ◽  
Large Pressure ◽  
Mass Action Law

A tool based on the mass action law was developed to calculate plasma compositions and thermodynamic properties for pure gases and mixtures, assuming a local thermodynamic equilibrium for pressures of up to 300 bar. The collection of the data that was necessary for tool calculation was automated by another tool that was written using Python, and the formats for the model were adapted directly from the NIST and JANAF websites. In order to calculate the plasma compositions for high pressures, virial correction was introduced. The influences of the parameters that were chosen to calculate the Lennard–Jones (12-6) potential were studied. The results at high pressure show the importance of virial correction for low temperatures and the dependence of the dataset used. Experimental data are necessary to determine a good dataset, and to obtain interaction potential. However, the data available in the literature were not always provided, so they are not well-adapted to a large pressure range. Due to this lack, the formulation provided by L. I. Stiel and G. Thodos (Journal of Chemical and Engineering Data, vol. 7, 1962, p. 234–236) is a good alternative when the considered pressure is not close to the critical point. The results may depend strongly on the system studied: examples using SF6 and CH4 plasma compositions are given at high pressure.

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