Rolling Moment Characteristic Analysis of Wrap-Around Fins

2010 ◽  
Vol 77 (5) ◽  
Author(s):  
Chen Xin-Hong ◽  
Zhao Run-Xiang
Keyword(s):  
Small Perturbation ◽  
Aerodynamic Characteristic ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Experimental Studies ◽  
Theoretical Method ◽  
Characteristic Analysis ◽  
Rolling Moment ◽  
Pressure Distributions ◽  
Perturbation Potential

A lot of numerical and experimental studies indicate that wrap-around fin configuration exhibits a self-induced rolling moment even at angle of attack zero. It depends on the unequal pressure distributions over both sides of the fin. In this paper, we try to prove this special aerodynamic characteristic with a theoretical method. According to the transonic small perturbation potential theory, as well as the transonic small perturbation potential equation, this paper found the expressions of the wrap-around fin convexity and the concave pressure coefficient at subsonic and supersonic by solving the Laplace equation and the Bessel function of imaginary argument, and analyze the phenomena of wrap-around fin rolling moment generation at angle of attack zero, and discuss the reason. The flow field of a projectile with wrap-around fins is solved by numerical method to check the pressure distributions of the two surfaces of the wing at subsonic and supersonic, respectively. The computational result is accordant to the theoretical analysis results. It is proved that the complicated pressure distribution of the wing surfaces leads to the particular characteristic of rolling moment.

Pressure measurements over a hemisphere-cylinder body attached with a forward facing spike

2013 ◽  
Vol 117 (1192) ◽  
pp. 639-646 ◽  
Author(s):  
R. Kalimuthu ◽  
R. C. Mehta ◽  
E. Rathakrishnan
Keyword(s):  
Shock Wave ◽  
Aerodynamic Drag ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Maximum Pressure ◽  
Geometrical Parameters ◽  
Pressure Measurements ◽  
Separation Region ◽  
Pressure Distributions ◽  
Oil Flow

AbstractThe present paper presents oil flow visualisations and pressure measurements over a hemisphere-cylinder body attached with a forward facing spike at Mach 6 and Reynolds number of 1·38 × 108at 0° and 5° angle-of-attack. The oil flow pictures depict the separation region in the vicinity of the spike on the hemisphere-cylinder body. The oil flow visualisations will help to locate the reattachment shock wave on the hemisphere-cylinder body and also understand the flow field behavior on the blunt-nosed spike configuration. The pressure measurements over the hemisphere-cylinder body depend on the shape and the length of the spike. The pressure distributions over the blunt-nosed body show significant influence of the angle-of-attack. The maximum pressure coefficient on the hemisphere-cylinder body is a function of the spike length, shape of the aerodisk and angle-of-attack. The windward and leeward sides pressure variations show dependence of the geometrical parameters of the spike and shape of the spike. The hemisphere and the flat-faced aerodisk cause considerable reduction of pressure leading to decrease of aerodynamic drag compared to the conical spike.

Interactions of a streamwise-oriented vortex with a finite wing

2015 ◽  
Vol 767 ◽  
pp. 782-810 ◽  
Author(s):  
D. J. Garmann ◽  
M. R. Visbal
Keyword(s):  
Separation Bubble ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Vortex ◽  
Recirculation Region ◽  
Rolling Moment ◽  
Effective Angle ◽  
Finite Wing ◽  
Modes Of Interaction

AbstractA canonical study is developed to investigate the unsteady interactions of a streamwise-oriented vortex impinging upon a finite surface using high-fidelity simulation. As a model problem, an analytically defined vortex superimposed on a free stream is convected towards an aspect-ratio-six ($\mathit{AR}=6$) plate oriented at an angle of ${\it\alpha}=4^{\circ }$ and Reynolds number of $\mathit{Re}=20\,000$ in order to characterize the unsteady modes of interaction resulting from different spanwise positions of the incoming vortex. Outboard, tip-aligned and inboard positioning are shown to produce three distinct flow regimes: when the vortex is positioned outboard of, but in close proximity to, the wingtip, it pairs with the tip vortex to form a dipole that propels itself away from the plate through mutual induction, and also leads to an enhancement of the tip vortex. When the incoming vortex is aligned with the wingtip, the tip vortex is initially strengthened by the proximity of the incident vortex, but both structures attenuate into the wake as instabilities arise in the pair’s feeding sheets from the entrainment of opposite-signed vorticity into either structure. Finally, when the incident vortex is positioned inboard of the wingtip, the vortex bifurcates in the time-mean sense with portions convecting above and below the wing, and the tip vortex is mostly suppressed. The time-mean bifurcation is actually a result of an unsteady spiralling instability in the vortex core that reorients the vortex as it impacts the leading edge, pinches off, and alternately attaches to either side of the wing. The increased effective angle of attack inboard of impingement enhances the three-dimensional recirculation region created by the separated boundary layer off the leading edge which draws fluid from the incident vortex inboard and diminishes its impact on the outboard section of the wing. The slight but remaining downwash present outboard of impingement reduces the effective angle of attack in that region, resulting in a small separation bubble on either side of the wing in the time-mean solution, effectively unloading the tip outboard of impingement and suppressing the tip vortex. All incident vortex positions provide substantial increases in the wing’s lift-to-drag ratio; however, significant sustained rolling moments also result. As the vortex is brought inboard, the rolling moment diminishes and eventually switches sign as the reduced outboard loading balances the augmented sectional lift inboard of impingement.

Theoretical and Experimental Study of Ship-Roll Stabilization Tanks

1968 ◽  
Vol 12 (03) ◽  
pp. 165-180
Author(s):  
W. H. Chu ◽  
J. F. Dalzell ◽  
J. E. Modisette
Keyword(s):  
Experimental Studies ◽  
Theoretical Method ◽  
Linear Control ◽  
Mathematical Representation ◽  
Control Element ◽  
Design Technique ◽  
Ship Roll ◽  
Roll Stabilization ◽  
Gross Behavior ◽  
Experimental Findings

This paper summarizes development of a quasi-linear theory for rectangular-type anti-rolling tank and presents results of the ensuing experimental investigation. Theoretical and experimental studies are compared. It was found that the initial theoretical method, although it reflects gross behavior of fluid in the tank and moments exerted on the ship therefrom, should be regarded as the foundation for a better understanding rather than as a design technique. Experimental findings indicate that the antiroll tank is a non-linear control element over its practical range of operation. Development of a nonlinear mathematical representation incorporating empirical results, as necessary, is recommended.

An Experimental Study of Fluid Flow in Disk Cavities

1992 ◽  
Vol 114 (2) ◽  
pp. 454-461 ◽  
Author(s):  
S. H. Bhavnani ◽  
J. M. Khodadadi ◽  
J. S. Goodling ◽  
J. Waggott
Keyword(s):  
Experimental Study ◽  
Fluid Flow ◽  
Gas Turbine ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Turbine Disk ◽  
Published Data ◽  
Disk System ◽  
Flow Rates ◽  
Pressure Distributions

Results are presented for an experimental study of fluid flow in models of gas turbine disk cavities. Experiments were performed on 70-cm-dia disks for rotational Reynolds numbers up to 2.29 × 106. Velocity and pressure distributions are presented and compared to previous theoretical and experimental studies for a free disk, and an unshrouded plane Rotor–Stator disk system. Minimum coolant flow rates for the prevention of ingress, determined for the case of a simple axial rim seal, compare well with previously published data.

scholarly journals Study of board bending degree on hydrodynamic performances of a single-layer cambered otter-board

2019 ◽  
Vol 131 ◽  
pp. 01120
Author(s):  
Lei Wang ◽  
Lu Min Wang ◽  
Yong Li Liu ◽  
Wen Wen Yu ◽  
Guang Rui Qi ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Single Layer ◽  
Moment Coefficient ◽  
Pitch Moment ◽  
Engineering Models ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The effect of board bending degree on hydrodynamic performances of a single-layer cambered otter-board was investigated using engineering models in a wind tunnel. Three different bending degree boards were evaluated at a wind speed of 28 m/s. Parameters measured included: drag coefficient Cx, lift coefficient Cy, pitch moment coefficient Cm, center of pressure coefficient Cp , over a range of angle of attack (0° to 70°). These coefficients were used in analyzing the differences in the performance among the three otter-board models. Results showed that the bending of the board(No. 2, No. 3) increased the water resistance of the otter-board, and improved the lift coefficient of the otter-board in the small angle of attack (0°<α≤20 °) ; the maximum lift coefficients Cy of otter-board model (No. 1) was higher (1.680, α = 25°). the maximum lift–drag ratios of models (No. 1, No. 2 and No. 3) are 6.822 (α = 7.5 °), 6.533 (α = 2.5 °) and 6.384 (α = 5.0°), which showed that the board bending reduces the lift-to-drag ratio of the otter-board.The stability of the No. 3 model was better than those two models (No. 1, No. 2) in most range of attack angle, but No. 1 otter-board model had a better stability in roll of otter-board. The findings of this study can offer useful reference data for the structural optimization of otter-boards for trawling.

A Method for Aerodynamic Characteristic Analysis of Hypersonic Aircraft Based on Response Surface Model

2013 ◽  
Vol 477-478 ◽  
pp. 277-280 ◽  
Author(s):  
Jie Yang ◽  
Song Ping Wu ◽  
Wen Xin Hou
Keyword(s):  
Flow Field ◽  
Response Surface ◽  
Aerodynamic Characteristic ◽  
Aerodynamic Characteristics ◽  
Surface Model ◽  
Complex Flow ◽  
Characteristic Analysis ◽  
Response Surface Models ◽  
Hypersonic Aircraft ◽  
Surface Models

Aerodynamic characteristic analysis of hypersonic cruise aircraft is more difficult than that of conventional aircraft, for the complex flow field simulation and inadequate amount of results under limited flight conditions. In this paper, numerical schemes applicable for hypersonic flow field are adopted to acquire a set of aerodynamic characteristics of a typical hypersonic cruise aircraft as sample data, based on which response surface models (RSM) are constructed to provide approximation of aerodynamic characteristics under any flight conditions within the design domain, finally the overall approximation performance of the response surface models are analyzed.

scholarly journals Normal forces exerted upon a long cylinder oscillating in an axial flow

2014 ◽  
Vol 752 ◽  
pp. 649-669 ◽  
Author(s):  
L. Divaret ◽  
O. Cadot ◽  
P. Moussou ◽  
O. Doaré
Keyword(s):  
Flow Velocity ◽  
Normal Force ◽  
Pressure Coefficient ◽  
Axial Flow ◽  
Fluid Forces ◽  
Normal Forces ◽  
Pressure Distributions ◽  
Damping Rate ◽  
Static Approach ◽  
Yaw Angle

AbstractThis work aims to improve understanding of the damping induced by an axial flow on a rigid cylinder undergoing small lateral oscillations within the framework of the quasistatic assumption. The study focuses on the normal force exerted on the cylinder for a Reynolds number of $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Re}=24\, 000$ (based on the cylinder diameter and axial flow velocity). Both dynamic and static approaches are investigated. With the static approach, fluid forces, pressure distributions and velocity fields are measured for different yaw angles and cylinder lengths in a wind tunnel. It is found that for yaw angles smaller than $5{^\circ }$, the normal force varies linearly with the angle and is fully dominated by its lift component. The lift originates from the high pressure coefficient at the front of the cylinder, which is found to depend linearly on the angle, and from a base pressure coefficient that remains close to zero independent of the yaw angle. At the base, a flow deficit and two counter-rotating vortices are observed. A numerical simulation using a $k\mbox{--}\omega $ shear stress transport turbulence model confirms the static experimental results. A dynamic experiment conducted in a water tunnel brings out damping-rate values during free oscillations of the cylinder. As expected from the linear dependence of the normal force on the yaw angle observed with the static approach, the damping rate increases linearly with the axial flow velocity. Satisfactory agreement is found between the two approaches.

Investigation of Supercritical Flow and Shape of Flip Bucket Spillways on Coefficients of Dynamic Pressure

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hessam Vatandoust ◽  
Hamidreza Yarmohammadi ◽  
Mohammadreza Kavianpour
Keyword(s):  
Froude Number ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Flow Speed ◽  
Middle Part ◽  
Statistical Characteristics ◽  
Pressure Coefficients

Abstract Pressure fluctuation is one of the major turbulent flow characteristics. It may cause crucial problems for hydraulic structures. This research is based on experimental studies, and it focuses on the measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. The function of the flip bucket spillway is discharging floods from reservoir dams which are energy storage source measurements of dynamic pressures on three different models of flip buckets that were performed for this investigation. Pressure fluctuation of the flip buckets have been measured within a range of Froude numbers from 5 to 13 (Fr = u/gy, where u is the flow speed, y is the depth, and g is 9.81 m/s2). Statistical characteristics of pressure fluctuations, the location, and the values of maximum and minimum fluctuations have also supplemented the study. The results show that the coefficients of pressure fluctuations (Cp = RMS/(0.5(u2/g)) where RMS is the root-mean-square of pressure fluctuation, u is the flow speed, and g is 9.81 m/s2) reduce as the Froude number (Fr) of flow increases, except a maximum Froude number. Pressure coefficients increase along the flip bucket with incremental mutations in the transformation area of the flip bucket. In the middle part of the flip bucket spillway, pressure coefficient values decrease. Additionally, as B/r (B is the width of the flip bucket and r is the radius of the flip bucket) ratio increases, pressure coefficients become larger and this process continues along the flip bucket.

Experimental investigation of pressure distribution characteristics of a flying-wing model using PSP

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040088
Author(s):  
Hongbiao Wang ◽  
Baoshan Zhu ◽  
Jian Xiong
Keyword(s):  
Pressure Distribution ◽  
Surface Pressure ◽  
Pressure Measurement ◽  
Pressure Coefficient ◽  
Leading Edge ◽  
Distribution Characteristics ◽  
Characteristic Analysis ◽  
Camera System ◽  
Wing Model ◽  
The Impact

To investigate the static pressure distribution characteristics of a flying-wing model, an advanced binary pressure sensitive paint (PSP) technique is introduced. It has low-temperature sensitivity and can compensate the errors induced by temperature. The pressure measurement test was performed in 0.6 m trisonic wind tunnel at angles of attack ranging from 0[Formula: see text] to 12[Formula: see text] in supersonic condition, adopting a low-aspect-ratio flying wing model. The binary PSP is sprayed on the upper surface of the model while pressure taps are installed on the upper surface of the right wing. Luminescent images of two probes are acquired with a color charge-coupled-device camera system and processed with calibration results. During the test, the surface pressure is measured by PSP and transducer, respectively. The results obtained show that the binary paint is of advantage to the surface pressure measurement and flow characteristic analysis. The high-resolution pressure spectra at different angle of attack clearly reveal the impact of leading edge vortex on the upper surface pressure distributions. The pressure measured by PSP also agrees well with the pressure tap results. The root mean square error of pressure coefficient is 0.01 at [Formula: see text], [Formula: see text].

Interference Effects of Wind Flow around Three Parallel-Aligned Wall-Mounted Cubes Placed in Turbulent Boundary Layer

2013 ◽  
Vol 805-806 ◽  
pp. 416-419
Author(s):  
Dan Gu ◽  
Hee Chang Lim
Keyword(s):  
Surface Pressure ◽  
Pressure Coefficient ◽  
Azimuth Angle ◽  
Wind Flow ◽  
Interference Effects ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Close Proximity ◽  
Flow Interference

The study undertook various calculations of the turbulent wind flow around a body in close proximity to neighboring obstacles, with the aim of gaining an understanding of the wind velocity and the surface-pressure variations with respect to the azimuth angle of wind direction and the gap distance between the obstacles. This paper presents the effects of wind flow interference among three parallel-aligned wall-mounted cubes for azimuth angles of Φ = 0°, 15°, 30°, and 45° and gap distances of G = 0.5h, 1.0h, 1.5h, and ∞ (i.e., a single cube), where G is the gap distance and h is the cube height. A transient detached eddy simulation (DES) was carried out to calculate the highly complicated wind flow domain around the three cubes to observe the surface-pressure, velocity, vortex and spectra characteristics. The results indicate that an increasing wind azimuth angle can even change the mean surface pressure coefficient on the side face of the center cube from negative to positive value. In addition, because of the interference effects, the velocity and pressure distributions around the center cube also show a substantial change depending on the gap distance.

Sign in / Sign up

Export Citation Format

Share Document