Aerodynamics and its application for vehicles / Járműáramlástan DIRECTIONAL STABILITY SIDE WIND EFFECT

Aerodynamics and its application for vehicles SIDE WIND EFFECT FORCES: LIFT force: L = c L (1/2rv 2 A) DRAG force: D = c D (1/2rv 2 A) SIDE(YAW) force: Y(S)= c Y (1/2rv 2 A) Lift-to-drag (L/D) ratio: L/D = c L /c D The lift-to-drag ratio is a measure of vehicle performance. For an aircraft, the higher the L/D ratio, the better is the vehicle (aircraft) performance. For gound vehicles, the higher the negative L/D ratio, the better is the vehicle stability since a high downforce (negative lift) is the goal for vehicle stability. COEFFICIENTS (based on FORCE): LIFT coeff.: c L = L / (1/2rv 2 A) DRAG coeff.: c D = D / (1/2rv 2 A) YAW coeff.: c Y = Y(S)/ (1/2rv 2 A) MOMENTS: PITCHING moment: M= c M (1/2rv 2 Ac) ROLLING moment: R = c R (1/2rv 2 Ac) YAWING moment: N = c N (1/2rv 2 Ac) c: traditionally the wing chord length, here (a;s;l) COEFFICIENTS (based on MOMENT): Coeff. of PITCHING moment: c M Coeff. of ROLLING moment: c R Coeff. of YAWING moment: c N Definitions of vehicle positions, forces and moments due to the airflow

Aerodynamics and its application for vehicles SIDE WIND EFFECT Definitions of vehicle positions, forces and moments due to the airflow

Aerodynamics and its application for vehicles SIDE WIND EFFECT Main origin of lift and pitching moment (But it is morely 3D effect!) Main origin of yawing moment (But it is morely 3D effect!)

Aerodynamics and its application for vehicles SIDE WIND EFFECT

Aerodynamics and its application for vehicles SIDE WIND EFFECT Drag and lift of cars as a function of angle of attack, a ; and, yawing angle, b

Aerodynamics and its application for vehicles SIDE WIND EFFECT

Aerodynamics and its application for vehicles INFLUENCE OF ADD-ON DEVICES (excrescences)

Aerodynamics and its application for vehicles EXCRESCENCES

Aerodynamics and its application for vehicles INFLUENCE OF WHEELS (TIRE WIDTH)

Aerodynamics and its application for vehicles GROUND PROXIMITY

Aerodynamics and its application for vehicles EXCRESCENCES

Aerodynamics and its application for vehicles CAR WITH TRAILER

Aerodynamics and its application for vehicles DETAIL OPTIMIZATION

Aerodynamics and its application for vehicles REAR SPOILER

Aerodynamics and its application for vehicles DETAIL OPTIMIZATION

Aerodynamics and its application for vehicles VEHICLE SOILING (by solid & liquid particles of natural & artificial origin) Primary-contamination particles: natural particles: rain drops, mist, dirt, mud etc. Foreing contamination particles natural particles: rain drops, mist, dirt, mud etc. Of upstrem vehicle artificial particles: exhaust gas with solid/liquid particles Self soiling windshield cleaning fluid, brake dust, exhaust gas with solid/liquid particles

Aerodynamics and its application for vehicles VEHICLE SOILING

Aerodynamics and its application for vehicles VEHICLE SOILING Soil deposition at the RUAG Aerospace wind tunnel used by Audi. Photo courtesy of Audi Results of water film forming on the front of an Audi car. Image courtesy of Audi and Icon Soil deposition at the rear of an Audi car. Image courtesy of Audi and Icon. Soil deposition on the tires of an Audi car. Image courtesy of Audi and Icon. Water droplets dispersing from an Audi car. Image courtesy of Audi and Icon

Aerodynamics and its application for vehicles VEHICLE SOILING

Aerodynamics and its application for vehicles VEHICLE SOILING Soil deposition at the RUAG Aerospace wind tunnel used by Audi. Photo courtesy of Audi Visualization of film thickness over time. Image courtesy of Audi and Icon

Aerodynamics and its application for vehicles VEHICLE SOILING

Aerodynamics and its application for vehicles VEHICLE SOILING This is a series of pictures that shows the vortex originating at the left side of the front window. From left to right that vortex is visualized by means of stream lines, stream ribbons and glyphs. With the aid of a slice probe, which maps the flow speed from blue (low) to red (high), you can see that the velocity inside a vortex is quite low as shown in the left picture. The cutting plane in the middle picture is used to localize areas of low (blue) and high pressure (red). Unsurprisingly, the pressure is especially high in front of the car and at the front window. By utilizing glyphs two or more scalar values can be encoded by a single three-dimensional arrow. In the right picture, for example, the velocity is represented by the length of the glyph, whereas the glyphs color is representing both pressure and total pressure in the flow (see paper for more information).

Aerodynamics and its application for vehicles VEHICLE SOILING The physically correct tracing of point masses enables us to perform soiling simulations with the animated particle probe system. The involved second order differential equations (PDEs) are solved by an embedded Runge-Kutta tracer of order 4(3). By applying an octree based collision detection the hit points on the car surface are visualized by a color change with red indicating highest dirtyness. The left picture shows a soiling simulation with dusty air. In the middle picture dirt particles were emitted by the front and back wheels of the car, thus simulating the car's self-soiling. In the right image dust particles were generated in the extent of the wireframe box behind the car leading to a dust distribution on the back of the car.

Aerodynamics and its application for vehicles VEHICLE SOILING

Aerodynamics and its application for vehicles VEHICLE SOILING In turbulent flows stream lines diverge quickly, so it is often very difficult to achieve a good understanding of the flow properties. Here animated particle probes offer a way to interactively trace a number of evolving particles that are generated by a stochastic process. In the above series, for example, the particle stream that is emitted from a small user-defined region behind the car keeps together for a small period of time but eventually splits into two rapidly diverging flows. One implicit advantage of animated particles is that the velocity can be viewed directly. In the samples above the color of the particle traces indicates their life time. On an SGI Octane MXI (2x250 MHz MIPS R10K processor) approximately 500 particles can be animated at a frame rate of 25 Hz. The particle tracing system scales nicely with the number of processors, thus the performance on an 8 processor SGI Onyx2 is quite impressive.

Aerodynamics and its application for vehicles VEHICLE SOILING A series of five images illustrating the soiling of a BMW 5 series touring. The dust distribution on the sides and the back of the car coincides well with real-world soiling evaluations conducted by BMW. As we are using a stationary flow for the soiling simulation we expect the results to become even better when migrating to instationary data sets.

Aerodynamics and its application for vehicles VEHICLE SOILING 1999-2003 1999-2003 2012

Aerodynamics and its application for vehicles CHECK THE CHANGE IN TILTING ANGLE / ROUNDING UP RADIUS (front, roof, back, A/C pillars)