scholarly journals Effect of porous baffle on sloshing pressure distribution in a barge mounted container subjected to regular wave excitation

2020 ◽  
Vol 17 (1) ◽  
pp. 1-30
Author(s):  
T. Nasar ◽  
S. A. Sannasiraj ◽  
V. Sundar
Keyword(s):  
Solid Wall ◽  
Porous Wall ◽  
Pressure Variation ◽  
Wave Excitation ◽  
Wave Flume ◽  
Liquid Depth ◽  
Side Walls ◽  
Porous Walls ◽  
Fill Level ◽  
Sloshing Pressure

An experimental study has been carried out to assess the sloshing pressure expected on the side walls of the tank and on top panel. A liquid fill level with an aspect ratio (hs /l, where hs is the static liquid depth and l is the tank length) of 0.488 is considered which corresponds to 75% liquid fill level. In view of suppressing sloshing oscillation and consequent sloshing pressure, the baffle wall configurations such as porous wall at l/2 and porous walls at l/3 and 2l/3 were adopted. Three porosities of 15%, 20.2%, and 25.2% were considered. The sloshing tank is fitted into the freely floating barge of model scale 1:43. The barge is kept inside the wave flume in the beam sea conditions. The effects of wave excitation frequencies and on the sloshing pressure variation have been studied in detail. For comparison purpose, solid wall placed at l/2 (Nasar and Sannasiraj, 2018) is also considered and, the salient results are herein reported.

Effect of Porous Baffle on Sloshing Pressure Distribution in a Barge Mounted Container Subjected to Wave Excitation

2017 ◽  
Author(s):  
Nasar Thuvanismail ◽  
Deepak J. Surahonne ◽  
Akshay P. Shah ◽  
Sannasiraj S. Annamalaisamy
Keyword(s):  
Experimental Study ◽  
Pressure Distribution ◽  
Pressure Variation ◽  
Wave Excitation ◽  
Wave Flume ◽  
Model Scale ◽  
Excitation Frequencies ◽  
Sloshing Pressure

An experimental study has been carried out to assess the sloshing pressure expected on the tank walls. Three porosities of 15%, 20.2%, 25.2% and baffle wall placed at center of tank is considered. The sloshing tank is fitted into the freely floating barge of model scale 1:43.The barge is kept inside the wave flume in the beam sea conditions. The effects of wave excitation frequencies and on the sloshing pressure variation have been studied in detail and, the salient results are herein reported.

On the theory of two-dimensional wind tunnels with porous walls

1955 ◽  
Vol 233 (1192) ◽  
pp. 74-90 ◽  
Keyword(s):  
Mach Number ◽  
Pressure Gradient ◽  
Solid Wall ◽  
Porous Wall ◽  
Effective Length ◽  
Wind Tunnels ◽  
Special Cases ◽  
Porous Surfaces ◽  
Independent Variable ◽  
Porous Walls

A mathematical theory is developed enabling wind tunnels with porous walls to be designed to give zero tunnel blockage in subsonic compressible flow. The tunnel walls are taken to be porous over only a finite range R , and solid elsewhere, and a sealed jacket is placed over the porous section so that the pressure on the outside of the porous wall can be controlled. The porous wall is assumed to have the characteristic that the component of velocity normal to it is proportional to the pressure drop across it, the constant of proportionality, λ, being termed the ‘porosity’ of the wail. Infinite porosity and zero porosity correspond to free streamline and solid wall boundaries respectively, which are thus included in the theory as special cases. The problem solved in this paper is to determine the relation between λ, R , the tunnel height H , and the Mach number M , so that the ‘blockage’, or velocity increment at the model caused by the tunnel walls, vanishes. It is found that for a given value of the porosity the length of the porous wall, R , must be reduced with increasing Mach number to keep the blockage zero. Thus the tunnel needs to be fitted with adjustable sections of solid wall which can be moved across the porous surfaces to reduce their effective length (see figure 1). Both ‘solid ’ and ‘wake’ blockage are considered in the paper. The effects of wake blockage, which are particularly important at high subsonic speeds due to the rapid increase in drag, cannot be completely eliminated by varying R alone. This is because wake blockage, unlike solid blockage, causes a pressure gradient in the tunnel. This gradient and the blockage can be eliminated simultaneously only by introducing a further independent variable. A very convenient one for this purpose can be created by pumping air at a certain rate from the jacket and exhausting it outside the tunnel. The rate of removal of the air from the jacket can be adjusted to eliminate the induced pressure gradient completely.

On the lifting aerofoil in a wind tunnel with porous walls

1957 ◽  
Vol 242 (1230) ◽  
pp. 341-354 ◽  
Keyword(s):  
Pressure Drop ◽  
Wind Tunnel ◽  
Average Velocity ◽  
Solid Wall ◽  
Porous Wall ◽  
Two Dimensional ◽  
Finite Range ◽  
Special Cases ◽  
Two Dimensional Flow ◽  
Porous Walls

The wind-tunnel corrections to the lift and moment acting on an aerofoil in a subsonic two-dimensional flow, and situated midway between tunnel walls containing porous sections are calculated. The tunnel walls are taken to be porous over only a finite range R , and solid else­where, and sealed jackets over the porous sections enable the pressures on the outsides of these sections to be controlled. The porous wall is assumed to be of such a construction that the component of velocity normal to it is proportional to the pressure drop across it. Infinite porosity and zero porosity correspond to free streamline and solid-wall boundaries respectively, which are thus included in the theory as special cases. This paper is complementary to an earlier contribution (Woods 1955 c ) in which only the ‘blockage’, or average velocity increment at the model caused by the tunnel walls, was studied.

The Motion of an Oscillating Aerofoil in a Compressible Free Jet

1956 ◽  
Vol 60 (549) ◽  
pp. 621-623 ◽  
Author(s):  
D. G. Drake
Keyword(s):  
Wind Tunnel ◽  
Solid Wall ◽  
Porous Wall ◽  
Present Problem ◽  
Normal Velocity ◽  
Free Jet ◽  
Porosity Parameter ◽  
Flow Past ◽  
Special Cases ◽  
Porous Walls

The supersonic and subsonic jets are both considered by the method used by Miles for an oscillating aerofoil between wind tunnel walls.The present problem and that of Miles are special cases of the flow past an oscillating aerofoil between porous walls, and provide a useful check for results in the porous wall problem. It may be assumed that the ratio of the change in pressure across a porous wall to the normal velocity at the wall defines a quantity called the porosity parameter, which is a constant at any particular point on the wall. For the special cases of the porosity parameter being everywhere infinite and zero, the porous wall corresponds to the solid wall and the free jet boundary respectively.

scholarly journals Turbulent channel flow over an anisotropic porous wall – drag increase and reduction

2018 ◽  
Vol 842 ◽  
pp. 381-394 ◽  
Author(s):  
Marco E. Rosti ◽  
Luca Brandt ◽  
Alfredo Pinelli
Keyword(s):  
Drag Reduction ◽  
Channel Flow ◽  
High Speed ◽  
Vertical Direction ◽  
Porous Wall ◽  
Turbulent Channel Flow ◽  
Spanwise Direction ◽  
Normal Velocity ◽  
Porous Walls ◽  
The One

The effect of the variations of the permeability tensor on the close-to-the-wall behaviour of a turbulent channel flow bounded by porous walls is explored using a set of direct numerical simulations. It is found that the total drag can be either reduced or increased by more than 20 % by adjusting the permeability directional properties. Drag reduction is achieved for the case of materials with permeability in the vertical direction lower than the one in the wall-parallel planes. This configuration limits the wall-normal velocity at the interface while promoting an increase of the tangential slip velocity leading to an almost ‘one-component’ turbulence where the low- and high-speed streak coherence is strongly enhanced. On the other hand, strong drag increase is found when high wall-normal and low wall-parallel permeabilities are prescribed. In this condition, the enhancement of the wall-normal fluctuations due to the reduced wall-blocking effect triggers the onset of structures which are strongly correlated in the spanwise direction, a phenomenon observed by other authors in flows over isotropic porous layers or over ribletted walls with large protrusion heights. The use of anisotropic porous walls for drag reduction is particularly attractive since equal gains can be achieved at different Reynolds numbers by rescaling the magnitude of the permeability only.

Liquid Sloshing Dynamics in a Container Subjected to Coupled Mode Excitation

2008 ◽  
Author(s):  
T. Nasar ◽  
S. A. Sannasiraj ◽  
V. Sundar
Keyword(s):  
Excitation Frequency ◽  
Qualitative Assessment ◽  
Floating Body ◽  
Nonlinear Behaviour ◽  
Wave Excitation ◽  
Coupled Mode ◽  
Sloshing Dynamics ◽  
Time Histories ◽  
Fill Level ◽  
The Individual

An experimental work has been carried out to study the phenomena of sloshing of liquid in a partially filled tank mounted on a barge exposed to regular beam waves. Liquid fill level with aspect ratio (hs/l, where hs is the static liquid depth and l is the tank length) of 0.325 is studied. The time histories of sloshing oscillation are measured along the length of container at predefined locations. The nonlinear behaviour of sloshing oscillation is observed for the regular wave excitation. The spectra of the sloshing oscillation and their qualitative assessment are reported. The individual sway and heave analytical model have been studied in order to substantiate the importance of coupled mode of excitation. Attempts are made to evaluate the harmonics present in the sloshing oscillation and compare with the results of earlier studies. In the present interaction study, it was found that the nonlinear response of the floating body also plays a role to induce violent sloshing oscillation. The effects of wave excitation frequency on the sloshing oscillation are reported.

Heat Transfer in a Channel with a Porous Wall for Turbine Cooling Application

1972 ◽  
Vol 94 (4) ◽  
pp. 385-390 ◽  
Author(s):  
L. L. Debruge ◽  
L. S. Han
Keyword(s):  
Solid Wall ◽  
Turbine Blades ◽  
Porous Plate ◽  
Porous Wall ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Turbine Cooling ◽  
Nusselt Numbers ◽  
Continuous Injection ◽  
Surface Temperature Variation

A method of cooling turbine blades internally by continuous injection through an interior baffle is analyzed. The analytical model consists of a two-dimensional channel formed by a solid wall (blade surface) and a porous plate (injection source). Based on incompressible- and laminar-flow assumptions, the velocity and the temperature fields are determined. The Nusselt numbers for a power-law surface-temperature variation are obtained and expressed in terms of the Prandtl and the Reynolds numbers. A related problem of cooling the turbine disk is also solved.

scholarly journals Stability of detonation in a circular pipe with porous walls

2012 ◽  
Vol 370 (1960) ◽  
pp. 668-688 ◽  
Author(s):  
Carlos Chiquete ◽  
Anatoli Tumin
Keyword(s):  
Boundary Condition ◽  
Stability Problem ◽  
Temporal Stability ◽  
Porous Wall ◽  
Circular Pipe ◽  
Normal Velocity ◽  
Point Boundary ◽  
Acoustic Boundary Condition ◽  
Porous Walls ◽  
The Stability

A stability analysis is carried out taking into account slightly porous walls in an idealized detonation confined to a circular pipe. The analysis is carried out using the normal-mode approach and corrections are obtained to the underlying impenetrable wall case results to account for the effect of the slight porosity. The porous walls are modelled by an acoustic boundary condition for the perturbations linking the normal velocity and the pressure components and thus replacing the conventional no-penetration boundary condition at the wall. This new boundary condition necessarily complicates the derivation of the stability problem with respect to the impenetrable wall case. However, exploiting the expressly slight porosity, the modified temporal stability can be determined as a two-point boundary value problem similar to the case of a non-porous wall.

scholarly journals Propagating Stall in Compressors With Porous Walls

1975 ◽  
Author(s):  
J. H. Horlock ◽  
C. M. Lakhwani
Keyword(s):  
Unsteady Flow ◽  
Radial Flow ◽  
Flow Instability ◽  
Porous Wall ◽  
Flow Coefficient ◽  
Compressor Blades ◽  
Axial Compressors ◽  
Flow Through ◽  
Porous Walls ◽  
End Wall

A modification is presented to the Emmons/Stenning analysis for predicting stall propagation, taking into account the unsteady flow through the end wall of a cascade row of compressor blades. It is shown that if radial flow from the blade channels is permitted, then the condition for flow instability is changed. The expression obtained for the flow coefficient at which stall occurs indicates an improvement in operating range, with virtually no effect on stall cell speed. Experimental evidence suggests that a mechanism such as that described may be the reason for the delay in stall onset produced by porous wall treatment of axial compressors.

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