scholarly journals CHANGES IN CURRENT PROPERTIES DUE TO WAVE SUPERIMPOSING

1986 ◽  
Vol 1 (20) ◽  
pp. 70 ◽  
Author(s):  
Toshiyuki Asano ◽  
Masahiro Nakagawa ◽  
Yuichi Iwagaki
Keyword(s):  
Shear Stress ◽  
Velocity Profile ◽  
Energy Conservation ◽  
Current Velocity ◽  
Conservation Equation ◽  
Bottom Shear Stress ◽  
Energy Conservation Equation ◽  
Friction Term ◽  
Mean Water Level ◽  
The Mean

Changes in current properties due to wave superimposing are investigated experimentally. Variations of the mean water level gradient and the current velocity profile after wave superimposing are examined. Experimental results are discussed in relation to the energy conservation equation including the bottom friction term. It is found that changes in current properties can be well explained by increase in the time averaged bottom shear stress.

Energy conservation, time-reversal invariance and reciprocity in ducts with flow

2001 ◽  
Vol 431 ◽  
pp. 223-237 ◽  
Author(s):  
WILLI MÖHRING
Keyword(s):  
Energy Conservation ◽  
Sound Wave ◽  
Conservation Equation ◽  
Smooth Transition ◽  
Rotational Flow ◽  
Flow Energy ◽  
Energy Conservation Equation ◽  
Reversal Invariance ◽  
Edge Conditions ◽  
Piecewise Continuous

A sound wave propagating in an inhomogeneous duct consisting of two semi-infinite uniform ducts with a smooth transition region in between and which carries a steady flow is considered. The duct walls may be rigid or compliant. For an irrotational sound wave it is shown that the three properties of the title are closely related, such that the validity of any two implies the validity of the third. Furthermore it is shown that the three properties are fulfilled for lossless locally reacting duct walls provided the impedance varies at most continuously. For piecewise-continuous wall properties edge conditions are essential. By an analytic continuation argument it is shown that reciprocity remains true for walls with loss. For rotational flow, energy conservation theorems have been derived only with the help of additional potential-like variables. The inter-relation between the three properties remains valid if one considers these additional variables to be known. If only the basic gasdynamic variables in both half-ducts are known, one cannot formulate an energy conservation equation; however, reciprocity is fulfilled.

Simulation of astrophysical flows in isentropic approximation

2018 ◽  
Vol 27 (10) ◽  
pp. 1844014
Author(s):  
S. G. Moiseenko ◽  
G. S. Bisnovatyi-Kogan
Keyword(s):  
Shock Wave ◽  
Kinetic Energy ◽  
Energy Conservation ◽  
Conservation Equation ◽  
Numerical Errors ◽  
Energy Conservation Equation ◽  
Different Types ◽  
Entropy Conservation ◽  
Isentropic Approximation ◽  
Astrophysical Flows

One of the difficulties of numerical simulations of cold supersonic astrophysical flows is a big difference in different types of energy. Gravitational and/or kinetic energy of the gas could be much larger than its internal energy. In such a case, it is possible to get large numerical errors in the simulations. To avoid this difficulty, conservation of entropy equation was used instead of energy conservation equation. The entropy conservation equation does not contain the gravitational and kinetic energy. The application of the isentropic set of equations is correct when the flow does not contain shocks or the amplitude of the shocks (shock wave Mach number) is not large. We estimate the violation of the energy conservation low when the “shock wave” is isentropic.

scholarly journals High-resolution velocity measurement in the inner part of turbulent boundary layers over super-hydrophobic surfaces

2016 ◽  
Vol 801 ◽  
pp. 670-703 ◽  
Author(s):  
Hangjian Ling ◽  
Siddarth Srinivasan ◽  
Kevin Golovin ◽  
Gareth H. McKinley ◽  
Anish Tuteja ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Velocity Profile ◽  
Drag Reduction ◽  
Slip Velocity ◽  
Reynolds Shear Stress ◽  
Turbulent Boundary Layers ◽  
Mean Velocity ◽  
Roughness Elements ◽  
The Mean

Digital holographic microscopy is used for characterizing the profiles of mean velocity, viscous and Reynolds shear stresses, as well as turbulence level in the inner part of turbulent boundary layers over several super-hydrophobic surfaces (SHSs) with varying roughness/texture characteristics. The friction Reynolds numbers vary from 693 to 4496, and the normalized root mean square values of roughness $(k_{rms}^{+})$ vary from 0.43 to 3.28. The wall shear stress is estimated from the sum of the viscous and Reynolds shear stress at the top of roughness elements and the slip velocity is obtained from the mean profile at the same elevation. For flow over SHSs with $k_{rms}^{+}<1$, drag reduction and an upward shift of the mean velocity profile occur, along with a mild increase in turbulence in the inner part of the boundary layer. As the roughness increases above $k_{rms}^{+}\sim 1$, the flow over the SHSs transitions from drag reduction, where the viscous stress dominates, to drag increase where the Reynolds shear stress becomes the primary contributor. For the present maximum value of $k_{rms}^{+}=3.28$, the inner region exhibits the characteristics of a rough wall boundary layer, including elevated wall friction and turbulence as well as a downward shift in the mean velocity profile. Increasing the pressure in the test facility to a level that compresses the air layer on the SHSs and exposes the protruding roughness elements reduces the extent of drag reduction. Aligning the roughness elements in the streamwise direction increases the drag reduction. For SHSs where the roughness effect is not dominant ($k_{rms}^{+}<1$), the present measurements confirm previous theoretical predictions of the relationships between drag reduction and slip velocity, allowing for both spanwise and streamwise slip contributions.

scholarly journals AN EXPERIMENT ON CLAY SUSPENSION UNDER WATER WAVES

1980 ◽  
Vol 1 (17) ◽  
pp. 171
Author(s):  
Prida Thimakorn
Keyword(s):  
Shear Stress ◽  
Water Waves ◽  
Equilibrium Concentration ◽  
Bottom Shear Stress ◽  
Clay Suspension ◽  
Average Value ◽  
Wave Channel ◽  
Maximum Value ◽  
The Mean ◽  
Short Time

The physical behaviour of water waves upon the suspension of fine cohesive clay was explored experimentally in a wave channel. Results obtained from the experiment show that equilibrium concentration is reached in the wave field some time about five hours after the initiation of waves. The ratio between the mean bottom concentration and the vertical average is constant and yields almost the same value within the range 1.17 and 1.34 at equilibrium and the bottom concentration at equilibrium is linearly proportioning to the maximum bottom velocity of waves. The dimensionless transient concentration possesses a relationship also with the bottom velocity and the bottom shear stress can be related to the maximum value of the ratio between the bottom concentration and the vertical average value found within a short time after the initiation of waves.

Dispersion and energy conservation relations of surface waves in semi-infinite plasma

1981 ◽  
Vol 25 (2) ◽  
pp. 285-307 ◽  
Author(s):  
V. Atanssov
Keyword(s):  
Surface Wave ◽  
Energy Conservation ◽  
Surface Waves ◽  
Low Frequency ◽  
Conservation Equation ◽  
Hydrodynamic Theory ◽  
Energy Conservation Equation ◽  
Surface Wave Propagation ◽  
Electric And Magnetic Fields ◽  
Bulk Waves

The hydrodynamic theory of surface wave propagation in semi-infinite homogeneous isotropic plasma is considered. Explicit linear surface wave solutions are given for the electric and magnetic fields, charge and current densities. These solutions are used to obtain the well-known dispersion relations and, together with the general energy conservation equation, to find appropriate definitions for the energy and the energy flow densities of surface waves. These densities are associated with the dispersion relation and the group velocity by formulae similar to those for bulk waves in infinite plasmas. Both cases of high-frequency (HF) and low-frequency (LF) surface waves are considered.

A Robust Three-Phase Isenthalpic Flash Algorithm Based on Free-Water Assumption

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Ruixue Li ◽  
Huazhou Andy Li
Keyword(s):  
Energy Conservation ◽  
Oil Recovery ◽  
Pure Water ◽  
Free Water ◽  
Conservation Equation ◽  
Feasible Region ◽  
Feed Mixture ◽  
Two Phase ◽  
Energy Conservation Equation ◽  
Three Phase

Isenthalpic flash is a type of flash calculation conducted at a given pressure and enthalpy for a feed mixture. Multiphase isenthalpic flash calculations are often required in compositional simulations of steam-based enhanced oil recovery methods. Based on a free-water assumption that the aqueous phase is pure water, a robust and efficient algorithm is developed to perform isenthalpic three-phase flashes. Assuming that the feed is stable, we first determine the temperature by solving the energy conservation equation. Then, the stability test on the feed mixture is conducted at the calculated temperature and the given pressure. If the mixture is found unstable, two-phase and three-phase vapor–liquid–aqueous isenthalpic flash can be simultaneously initiated without resorting to stability tests. The outer loop is used to update the temperature by solving the energy conservation equation. The inner loop determines the phase fractions and compositions through a three-phase free-water isothermal flash. A two-phase isothermal flash will be initiated if an open feasible region in the phase fractions appears in any iteration during the three-phase flash or any of the ultimately calculated phase fractions from the three-phase flash do not belong to [0,1]. A number of example calculations for water/hydrocarbon mixtures are carried out, demonstrating that the proposed algorithm is accurate, efficient, and robust.

scholarly journals An Energy Conservation Algorithm for Nonlinear Dynamic Equation

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Jian Pang ◽  
Yu Du ◽  
Ping Hu ◽  
Weidong Li ◽  
Z. D. Ma
Keyword(s):  
Energy Conservation ◽  
Nonlinear Problems ◽  
Current Method ◽  
Conservation Equation ◽  
Iteration Formula ◽  
Energy Conservation Equation ◽  
Numerical Result ◽  
Nonlinear Dynamic Equation ◽  
Runge Kutta Method ◽  
Runge Kutta

An energy conservation algorithm for numerically solving nonlinear multidegree-of-freedom (MDOF) dynamic equations is proposed. Firstly, by Taylor expansion and Duhamel integration, an integral iteration formula for numerically solving the nonlinear problems can be achieved. However, this formula still includes a parameter that is to be determined. Secondly, through some mathematical manipulations, the original dynamical equation can be further converted into an energy conservation equation which can then be used to determine the unknown parameter. Finally, an accurate numerical result for the nonlinear problem is achieved by substituting this parameter into the integral iteration formula. Several examples are used to compare the current method with the well-known Runge-Kutta method. They all show that the energy conservation algorithm introduced in this study can eliminate algorithm damping inherent in the Runge-Kutta algorithm and also has better stability for large integral steps.

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