Approach to side force alleviation through modification of the pointed forebody geometry

1990 ◽  
Author(s):  
V. MODI ◽  
A. STEWART
Keyword(s):  
Side Force

Lateral Tire Forces on Wet Roads

1977 ◽  
Vol 5 (2) ◽  
pp. 75-82 ◽  
Author(s):  
A. Schallamach
Keyword(s):  
Normal Load ◽  
The Self ◽  
Experimental Results ◽  
Slip Angle ◽  
Tire Model ◽  
Side Force ◽  
Tire Forces

Abstract Expressions are derived for side force and self-aligning torque of a simple tire model on wet roads with velocity-dependent friction. The results agree qualitatively with experimental results at moderate speeds. In particular, the theory correctly predicts that the self-aligning torque can become negative under easily realizable circumstances. The slip angle at which the torque reverses sign should increase with the normal load.

scholarly journals Numerical Investigation on the Influence of the Streamlined Structures of the High-Speed Train’s Nose on Aerodynamic Performances

2021 ◽  
Vol 11 (2) ◽  
pp. 784
Author(s):  
Zhenxu Sun ◽  
Shuanbao Yao ◽  
Lianyi Wei ◽  
Yongfang Yao ◽  
Guowei Yang
Keyword(s):  
Drag Reduction ◽  
Pressure Distribution ◽  
Flow Separation ◽  
High Speed ◽  
Leeward Side ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Asymmetrical Design

The structural design of the streamlined shape is the basis for high-speed train aerodynamic design. With use of the delayed detached-eddy simulation (DDES) method, the influence of four different structural types of the streamlined shape on aerodynamic performance and flow mechanism was investigated. These four designs were chosen elaborately, including a double-arch ellipsoid shape, a single-arch ellipsoid shape, a spindle shape with a front cowcatcher and a double-arch wide-flat shape. Two different running scenes, trains running in the open air or in crosswind conditions, were considered. Results reveal that when dealing with drag reduction of the whole train running in the open air, it needs to take into account how air resistance is distributed on both noses and then deal with them both rather than adjust only the head or the tail. An asymmetrical design is feasible with the head being a single-arch ellipsoid and the tail being a spindle with a front cowcatcher to achieve the minimum drag reduction. The single-arch ellipsoid design on both noses could aid in moderating the transverse amplitude of the side force on the tail resulting from the asymmetrical vortex structures in the flow field behind the tail. When crosswind is considered, the pressure distribution on the train surface becomes more disturbed, resulting in the increase of the side force and lift. The current study reveals that the double-arch wide-flat streamlined design helps to alleviate the side force and lift on both noses. The magnitude of side force on the head is 10 times as large as that on the tail while the lift on the head is slightly above that on the tail. Change of positions where flow separation takes place on the streamlined part is the main cause that leads to the opposite behaviors of pressure distribution on the head and on the tail. Under the influence of the ambient wind, flow separation occurs about distinct positions on the train surface and intricate vortices are generated at the leeward side, which add to the aerodynamic loads on the train in crosswind conditions. These results could help gain insight on choosing a most suitable streamlined shape under specific running conditions and acquiring a universal optimum nose shape as well.

Drifting Force and Moment on Ships in Oblique Waves

1966 ◽  
Vol 10 (01) ◽  
pp. 18-24
Author(s):  
Pung Nien Hu ◽  
King Eng
Keyword(s):  
Potential Theory ◽  
General Expression ◽  
Phase Angle ◽  
Analytical Solutions ◽  
Vertical Axis ◽  
Long Waves ◽  
Elementary Functions ◽  
Oblique Waves ◽  
Side Force ◽  
Yaw Moment

A general expression for the drifting moment about the vertical axis of an oscillating ship in regular oblique waves is derived from the potential theory, following a similar procedure developed by Maruo for drifting force. Explicit analytical solutions for the drifting side force and yaw moment on thin ships in long waves are obtained in terms of simple elementary functions. The effect of the wave frequency, the draft of the ship, the displacement, and the phase angle of the ship oscillation are discussed.

Theoretical Tire Model Considering Two-Dimensional Contact Patch for Force and Moment

2021 ◽  
Author(s):  
Y. Nakajima ◽  
S. Hidano
Keyword(s):  
Finite Element Method ◽  
Shear Force ◽  
The Self ◽  
Slip Angle ◽  
Force Distribution ◽  
Two Dimensional ◽  
Tire Model ◽  
Side Force ◽  
Contact Patch ◽  
Proposed Model

ABSTRACT The new theoretical tire model for force and moment has been developed by considering a two-dimensional contact patch of a tire with rib pattern. The force and moment are compared with the calculation by finite element method (FEM). The side force predicted by the theoretical tire model is somewhat undervalued as compared with the FEM calculation, while the self-aligning torque predicted by the theoretical tire model agrees well with the FEM calculation. The shear force distribution in a two-dimensional contact patch under slip angle predicted by the proposed model qualitatively agrees with the FEM calculation. Furthermore, the distribution of the adhesion region and sliding region in a two-dimensional contact patch predicted by the theoretical tire model qualitatively agrees with the FEM calculation.

Strakes Effects on Asymmetric Flow Over a Blunt-Nosed Slender Body at a High Angle of Attack

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Qihang Yuan ◽  
Yankui Wang ◽  
Zhongyang Qi
Keyword(s):  
Angle Of Attack ◽  
Slender Body ◽  
Axial Position ◽  
High Angle ◽  
Asymmetric Flow ◽  
High Angle Of Attack ◽  
Side Force ◽  
Asymmetric Vortices ◽  
High Angles Of Attack ◽  
Blunt Nose

In general speaking, the missiles execute flight at high angles of attack in order to enhance their maneuverability. However, the inevitable side-force, which is caused by the asymmetric flow over these kinds of traditional slender body configurations with blunt nose at a high attack angle, induces the yawing or rolling deviation and the missiles will lose their predicted trajectory consequently. This study examines and diminishes the side-force induced by the inevitable asymmetric flow around this traditional slender body configuration with blunt nose at a high angle of attack (AoA = 50 deg). On one hand, the flow over a fixed blunt-nosed slender body model with strakes mounted at an axial position of x/D = 1.6–2.7 is investigated experimentally at α = 50 deg (D is the diameter of the model). On the other hand, the wingspan of the strakes is varied to investigate its effect on the leeward flow over the model. The Reynolds number is set at ReD = 1.54 × 105 based on D and incoming upstream velocity. The results verify that the formation of asymmetric vortices is hindered by the existence of strakes, and the strake-induced vortices develop symmetrically and contribute to the reduction in side-force of the model. In addition, the increase in strake wingspan reduces asymmetric characteristics of the vortex around the model and causes a significant decrease in side-force in each section measured. The strake with the 0.1D wingspan can reduce the sectional side-force to 25% of that in the condition without strakes.

Some difficulties associated with the limit equilibrium method of slices

1983 ◽  
Vol 20 (4) ◽  
pp. 661-672 ◽  
Author(s):  
R. K. H. Ching ◽  
D. G. Fredlund
Keyword(s):  
Slope Stability ◽  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Stability Limit ◽  
Limit Equilibrium Method ◽  
Soil Conditions ◽  
Side Force ◽  
Limit Equilibrium Methods ◽  
Equilibrium Method ◽  
The Stability

Several commonly encountered problems associated with the limit equilibrium methods of slices are discussed. These problems are primarily related to the assumptions used to render the inherently indeterminate analysis determinate. When these problems occur in the stability computations, unreasonable solutions are often obtained. It appears that problems occur mainly in situations where the assumption to render the analysis determinate seriously departs from realistic soil conditions. These problems should not, in general, discourage the use of the method of slices. Example problems are presented to illustrate these difficulties and suggestions are proposed to resolve these problems. Keywords: slope stability, limit equilibrium, method of slices, factor of safety, side force function.

scholarly journals ANALISIS MOMEN POROS DAN GAYA SAMPING HORN RUDDER BIDANG KENDALI PESAWAT N-XXX MENGGUNAKAN COMPUTATIONAL FLUID DYNAMIC

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Muchammad Muchammad
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Side Force

Pesawat merupakan sarana transportasi yang memiliki arti penting bagi pembangunan ekonomi dan pertahanan, mengingat bahwa Indonesia adalah sebuah Negara kepulauan dengan kondisi geografis yang sulit untuk diakses tanpa sarana transportasi yang memadai. Penelitian ini bertujuan agar mendapatkan koefisiean hinge moment dan side force bidang kendali ekor pesawat N-XXX pada bagian rudder horn dengan variasi defleksi dengan derajat tertentu. Metode yang digunakan untuk analisis aerodinamika ada beberapa macam, yakni metode analisis Computational Fluid Dynamic (CFD) dan eksperimen yang biasa dilakukan dengan uji terowongan angin yang menawarkan tingkat keakuratan hasil lebih nyata namun dengan biaya yang lebih besar. Metode yang digunakan pada penelitian ini adalah analisis dengan metode Computational Fluid Dynamic (CFD). Penelitian dilakukan dengan variasi defleksi pada horn rudder sebesar 0°,10°,20° untuk mengetahui nilai hinge moment dan side force dengan langkah mengidealisasi geometri, meshing dan diselesaikan dengan CFD untuk perhitungannya guna mendapatkan nilai hinge moment dan side force. Pada defleksi 0° mempunyai nilai hinge moment -0.588, defleksi 10° mempunyai nilai hinge moment 0.653 dan defleksi 20° mempunyai nilai hinge moment -3.836 sedangkan untuk nilai side force pada  defleksi 0° mempunyai nilai side force -0.999, defleksi pada 10° mempunyai nilai side force 70.908, defleksi 20° mempunyai nilai side force 106.773.Kata kunci: ekor pesawat, defleksi, hinge moment, rudder horn, side force.

Experimental Investigation of a Drafting Cyclist in Cross-Wind

2017 ◽  
Author(s):  
Ivaylo Nedyalkov ◽  
Adam Lovell ◽  
Alec Cunningham
Keyword(s):  
Experimental Investigation ◽  
Wind Tunnel ◽  
3D Model ◽  
Noticeable Effect ◽  
Side Force ◽  
Scale Models ◽  
Competitive Cyclists

Drafting is commonly utilized in cycling, particularly during competitions. According to the literature, in a racing environment, the riders can expend 90% of their energy on overcoming drag, and can save about 30% of their energy by riding behind another rider in the absence of cross-wind. In the presence of a strong cross-wind, competitive cyclists form echelons by placing themselves about halfway behind each other, while being slightly offset sideways. Although forming an echelon is a common practice, the formation has not been sufficiently studied in the literature. To address this, the drag and side forces on a model cyclist were studied experimentally. A simplified 3D model was built based on the outline of a competitive cyclist. Two 1:11 scale models were rapid-prototyped and tested in a wind tunnel. The drafting effects on a cyclist were investigated for different yaw angles — the angles of the apparent wind with respect to the direction of cyclist motion. The effects of wind-stream-wise position and wind-off-stream-wise position were studied for each angle by measuring the drag and side-force on a model placed in the wake of another identical model. The results suggest that there is a significant decrease in both drag and side force when a cyclist is riding in the wake of another cyclist. Although a smaller wind-stream-wise offset generally results in smaller forces, this effect is not significant for most configurations. The offset in the wind-off-stream-wise direction has a noticeable effect on the forces — no off-stream-wise offset results in the lowest drag and side force, except for low yaw angles at which it may be beneficial for the drafting cyclist to be slightly forward with respect to the in-line (no offset) position.

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