Computations and measurements of the global drag force on a Tension-Leg Platform

2021 ◽  
Vol 239 ◽  
pp. 109710
Author(s):  
S.S. Dai ◽  
J.R. Chaplin ◽  
B.A. Younis ◽  
D. Tang ◽  
T.L. Zhai
Keyword(s):  
Drag Force ◽  
Tension Leg Platform

Stochastic Response of a Tension Leg Platform to Viscous Drift Forces

1991 ◽  
Vol 113 (2) ◽  
pp. 148-155 ◽  
Author(s):  
M. G. Donley ◽  
P. D. Spanos
Keyword(s):  
Drag Force ◽  
Volterra Series ◽  
Viscous Force ◽  
Stochastic Response ◽  
Tension Leg Platform ◽  
Stochastic Linearization ◽  
Gaussian Probability Distribution ◽  
The One ◽  
Non Gaussian ◽  
Three Degree Of Freedom

A stochastic analysis of a tension leg platform subjected to wave and current loads is performed. The viscous force is modeled by the nonlinear Morison equation drag force term. As an improvement to equivalent stochastic linearization of the drag force, an equivalent stochastic “quadratization” method is proposed, in which the drag force nonlinearity is replaced by an “equivalent” quadratic nonlinearity. The resulting nonlinear equivalent system is in a form which can be solved approximately by a Volterra series expansion. The non-Gaussian probability distribution of the response is approximated by a Gram-Charlier expansion. The method is applied on a three degree-of-freedom model. The power spectrum of the response determined by the proposed method compares well with the one obtained by a Monte-Carlo simulation.

Experimental Study of Flow Control Over a Standard Road Vehicle Using Plasma Actuator

2020 ◽  
Vol 22 (4) ◽  
pp. 1047-1060
Author(s):  
S. Shadmani ◽  
S. M. Mousavi Nainiyan ◽  
R. Ghasemiasl ◽  
M. Mirzaei ◽  
S. G. Pouryoussefi
Keyword(s):  
Flow Control ◽  
Pressure Distribution ◽  
Drag Force ◽  
Separated Flow ◽  
Plasma Actuator ◽  
Road Vehicle ◽  
Slant Angle ◽  
Total Drag ◽  
Slant Surface ◽  
Ahmed Body

AbstractAhmed Body is a standard and simplified shape of a road vehicle that's rear part has an important role in flow structure and it's drag force. In this paper flow control around the Ahmed body with the rear slant angle of 25° studied by using the plasma actuator system situated in middle of the rear slant surface. Experiments conducted in a wind tunnel in two free stream velocities of U = 10m/s and U = 20m/s using steady and unsteady excitations. Pressure distribution and total drag force were measured and smoke flow visualization carried out in this study. The results showed that at U = 10m/s using plasma actuator suppress the separated flow over the rear slant slightly and be effective on pressure distribution. Also, total drag force reduces in steady and unsteady excitations for 3.65% and 2.44%, respectively. At U = 20m/s, using plasma actuator had no serious effect on the pressure distribution and total drag force.

OUTDOOR TESTS OF A TOWED BOAT MODEL WITH FUEL COMBUSTION IN A BOTTOM CAVITY

2020 ◽  
Author(s):  
S. M. FROLOV ◽  
◽  
S. V. Platonov ◽  
K. A. AVDEEV ◽  
V. S. AKSENOV ◽  
...  
Keyword(s):  
Drag Force ◽  
Direct Contact ◽  
Propulsion System ◽  
Hydrodynamic Drag ◽  
Atmospheric Air ◽  
System A ◽  
Bottom Cavity ◽  
Gas Cavity ◽  
System Power ◽  
Gas Supply

To reduce the hydrodynamic drag force to the movement of the boat, an artificial gas cavity is organized under its bottom. Such a cavity partially insulates the bottom from direct contact with water and provides “gas lubrication” by means of forced supply of atmospheric air or exhaust gases from the main propulsion system. A proper longitudinal and transverse shaping of the gas cavity can significantly (by 20%-30%) reduce the hydrodynamic drag of the boat at low (less than 3%) consumption of the propulsion system power for gas supply.

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