Flow-Induced Forces on an Inclined Square Cylinder (original) (raw)

Mean viscous drift forces on a fixed vertical cylinder in waves and currents

Journal of the Korea Academia Industrial Cooperation Society, 2020

In offshore structures, the mean viscous drift force due to drag is considered to be a design part that has not been considered until recently. In particular, it is most important to calculate the drift force acting on a vertical cylinder considering both waves and currents in the low frequency region. This paper presents a process for deriving analytical solutions for the drift forces acting on a fixed vertical cylinder considering waves and currents. The area of the cylinder was considered by dividing it into a splash zone above the free surface and a submerged zone below the free surface. The presence of waves is considered only in the Splash Zone, and in the case of waves and currents, the equations were obtained for both the splash and submerged zones. The results show that drift forces occur due to the significant viscous effects in both the splash zone and the submerged zone. Therefore, the analytical solutions derived in this study can be used to calculate the drift force us...

사이클론 청소기 내부 유동에 관한 수치해석적 연구

Clean Technology, 2014

General household vacuum cleaners consist of dust collector, pre filter, motor and exhaust filter, and the filtered clean air is discharged to the atmosphere. By using the CFD methods, we estimated the internal flow in two types of commercial cyclone vacuum cleaners to evaluate the dust collection performance. From the analysis, it was known that the number of revolution had higher values in cyclone cone region. CFD analysis in a specific showed non-uniform velocity distribution at outlet, which results in the deterioration of particle collection performance. In order to improve flow condition, the installation of baffle was proposed and the values of velocity RMS were estimated.

회전 효과를 고려한 Active Gurney Flap 의 동특성 해석

Transactions of the KSME C: Industrial Technology and Innovation, 2015

In this study, the finite element analysis was carried out to investigate dynamic characteristics of the AGF(Active Gurney Flap) which is under development for reducing vibration and noise of the helicopter rotor system. The Gurney flap is a kind of small flat plate, mounted normal to the lower surface of the airfoil near to the trailing edge. An electric motor, L-shaped linkages and flap parts were integrated into a rotor bade, and 3~5/rev control was given to the AGF to reduce the vibration in the fixed frame. Thus, an explicit time integration method was adopted to investigate the dynamic response of the AGF with considering both centrifugal force due to the rotor rotation and active control input, and it can be seen that the vertical displacement of the AGF was satisfied to meet the design requirement.

Hydrodynamic Aspects on Three-dimensional Effects of Vertical-axis Tidal Stream Turbine

한국해양환경 에너지학회지, 2013

Hydrodynamic aspects on three-dimensional effects were investigated in this study for simple and convenient conversion of tidal stream energy using a Vertical-Axis Turbine (VAT). Numerical approach was made to reveal the differences of flow physics between 2-D estimation and rigorous 3-D simulation. It was shown that the 3-D effects were dominant mainly due to the variation of tip vortices around the tip region of rotor blade, causing the loss of lift for steadily translating hydrofoil and the reduction of torque for rotating turbine blade. The 3-D effect was found to be rather prominent for the typical VATs considered in this paper. Simple and yet efficient 2-D approach with the correction of its three-dimensionality was also proposed for practical design and analysis of VAT.

Theoretical and Computation Analysis on the Pressure Drop in the Cyclone Dust Collector

Clean Technology, 2014

Using the CFD method, the pressure drop in 6 cyclone dust collectors of different shape were calculated. And the results were compared with results of the conventional theories. Equations of Shepherd and Lapple (1939, 1940), First (1950), Alexander (1949), Stairmand (1949), Barth (1956) were used in the theoretical calculation. In CFD calculations, we used standard k-epsilon model for analysis of turbulent flow, fluid is 25 ℃ air, the velocity at inlet is 10 m/s and the temperature is 25 ℃. In CFD analysis results, the pressure distributions along the flow showed similar patterns in different cyclone shapes. But the pressure drop distributions estimated on the conventional theories had big difference in different cyclone shapes. Only First's theory and CFD analysis showed similar results.

Strong Hamiltonicity of Recursive Circulants

Journal of KIISE:Computer Systems and Theory, 2001

In this paper, we investigate strong hamiltonian properties of recursive circulant G(2m,2k) from the graph theory point of view. Recursive circulant is an interconnection structure for multicomputer networks proposed in [9]. We consider the problem whether G(2m,2k) has a path of length l joining a pair of vortices v and H, and show that (a) G(2m,2) has a path of length l forany l≥d(w,w), (b) G(2m,4) has a path of length l for any l≥d(v,w) + 2, (c) for some pair of vertices in G(2m,2k), k≥3, there is no path of length d(v, w) + 2k-3, where d(v, w) is the distance from v to w.

A Study on the Vibration Characteristics of Bolted Plates Depending on the Clamping Force of the Bolt

Transactions of the Korean Society for Noise and Vibration Engineering, 2022

The vibration characteristics of bolted structures change depending on the bolt's clamping force. This can be used to detect bolt looseness or to evaluate structural integrity. In this study, the vibration characteristics based on a bolt's clamping force were experimentally and numerically studied in two plate structures connected using a bolt; where the clamping force ranged from 60 % to 100 %

Optimal Design of Impeller Shroud for Centrifugal Compressor Using Response Surface Method

The KSFM Journal of Fluid Machinery, 2015

In this study, a method for optimal design of impeller shroud for centrifugal compressor using response surface method (RSM) and multi-objective genetic algorithm (MOGA) was studied. Numerical simulation was conducted using ANSYS CFX with various configurations of shroud. Each of the design parameters was divided into 3 levels. Total 15 design points were planned by central composite design (CCD) method, which is one of the design of experiment (DOE) techniques. Response surfaces based on the results of DOE were used to find the optimal shape of impeller shroud for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design Xplorer (DX). Results showed that the isentropic efficiency, which is the main performance parameter of the centrifugal compressor, was increased 0.4% through the optimization.

압전 작동기를 이용한 방향 제어 밸브의 동적 모델링 및 제어

Transactions of the Korean Society for Noise and Vibration Engineering, 2012

This paper proposes a new type of high-frequency directional valve controlled by the piezostack actuator associated with displacement amplifier. As a first step, a dynamic model of directional valve which can operate at 200 Hz with a flow rate of 12 litter/min is derived by considering pressure drop and flow force. As a second step, an appropriate piezostack is selected by considering actuation force as well as field-dependent displacement. Subsequently, in order to control spool displacement and flow rate a proportional-derivative(PD) controller is designed based on the 3rd-order valve

Experimental Study on the Velocity Structure of 2-D Density Current Induced by Selective Withdrawal

2009

A series of laboratory experiments has been performed to investigate the flow characteristics of 2-dimensional density currents induced by selective withdrawal, which is commonly suggested as a measure for removal of high turbid water from reservoirs. Saltwater has been used to simulate the density stratification over depth and PIV(Particel Image Velocimetry) for observing the velocity structure. Experimental conditions have been established according to Richardson number, which is the dimensionless number that expresses the ratio of potential to kinetic energy. From the experiments, the patterns of longitudinal decay of centerline axial velocity induced by the withdrawal have been distinguished from other experimental cases. The rate of longitudinal decay increase as the Richardson number increases. The variations of volumetric and momentum flux along the longitudinal axis have also shown to be dependent on Richardson number.