FLOW CONTROL

FIELD OF THE INVENTION

The present invention relates generally to automobile aerodynamics. More specifically, the present invention is a low drag low noise automobile mirror using passive jet flow control, which is specifically designed to reduce the level of both drag and noise that are normally produced by the rear view side mirrors commonly found on automobiles, including cars, trucks, motorcycles, boats, locomotives, airplanes, etc.

BACKGROUND OF THE INVENTION

Automobiles and motor vehicles, including cars, trucks, motorcycles, boats, locomotives, airplanes, and their combination, etc, have emerged as the dominant from of human transportation in the modern world. Motor vehicles are capable of transporting a human operator and passengers over great distances at great speeds when compared to older forms of transportation. The range of travelling speed for a motor vehicle on roads, water or air is typically anywhere from ten miles an hour up to above four hundred miles an hour. These speeds are enough to cause significant flow or

aerodynamic drag on the motor vehicles. As a result of this, most motor vehicles posses specifically designed bodies that utilize the concepts of fluid dynamics in order to direct the flow through which the motor vehicle travels with drag as low as possible.

A very significant part of flow drag of a motor vehicle is from its external mirrors due to the low base pressure behind the mirror surfaces. A few examples of the common shape of rear view mirrors can be seen in FIG. 1, FIG. 2, and FIG. 3. The rear view mirrors are exposed to the incoming flow and are usually installed outside of the vehicle cabins that hold the operator and the occupants. This drag causes fuel consumption of the vehicle since the engine needs to generate the thrust to overcome the drag. Drag created by external mirrors is a very significant part of the total drag of a motor vehicle, especially for smaller and lighter vehicles (e,g, electric cars, Formula 1, Smart, Mini Cooper, etc) or heavy load trucks, which have relatively large ratio of the mirror area to the overall captured area. Lighter and smaller cars have become more and more popular as they tend to get better fuel mileage and be more environmentally friendly. Heavy load trucks are crucial for long distance transportation of goods. Mirror drag reduction hence will substantially contribute to reducing global fuel and energy consumption and emission pollution. Apart from drag force, another important issue to consider when a motor vehicle travels through a fluid such as air at a certain speed is noise. A lot of the noise that the operator and the occupants hear when driving a motor vehicle is in fact from flow around the motor vehicle. In particular, the external rear view mirrors are one of the major sources of noise.

The flow conditions responsible for generating both the high drag and high noise from the external mirrors are vortex shedding that generates low base pressure behind the mirror surfaces and high turbulence pressure fluctuation. An example of how the vortex shedding may occur with a common side view mirror can be seen in FIG. 4, which illustrates the streamlines around a rear view mirror. These flow conditions are a result of the fact that the side view mirror has a streamlined front and then abruptly terminates with a flat back, which is the mirror surface used by the operator to view areas behind the motor vehicle. The vortex shedding and the associated low pressure and high turbulence pressure fluctuations are the direct result of the side view mirror having a flat back that creates an overall flow condition referred to as a base flow.

The base flow as described above is the primary source of drag and noise associated with side view mirrors. The noise can be very annoying to occupants of the vehicle and affect their audibility of music and conversation. Noise level inside a motor vehicle can especially be severe with smaller and lighter vehicles, which often have thinner bodies and doors to help reduce weight and increase fuel efficiency. The thinner bodies and doors make it easier for the noise to penetrate into the motor vehicles. The objective of the present invention is to introduce a low drag low noise automobile mirror design concept using jet flow control that serves to reduce the effects of the base flow vortex shedding, and thereby reduce the noise and drag caused by the rear view mirror while maintaining an unobstructed view of the mirror. The present invention achieves significant reduction of drag and noise by manipulating the flow around the side view mirror to create directed jets of air around the flat mirror surface to form a virtual trailing edge to remove vortex shedding that causes the drag and noise. The present invention is aimed at reducing aerodynamic drag and noise, but can be also applied to other fluids such as water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a current motor vehicle external rear view mirror.

FIG. 2 is a perspective view of another current motor vehicle external rear view mirror. FIG. 3 is a perspective view of another current motor vehicle external rear view mirror. FIG. 4 is a side view of streamlines of a typical motor vehicle external rear view mirror subjected to a flow field, thus depicting how typical motor vehicle external rear view mirrors cause vortex shedding.

FIG. 5 is a perspective view of the first embodiment of the present invention;

FIG. 6 is a front view thereof;

FIG. 7 is a right side view thereof;

FIG. 8 is a rear view thereof;

FIG. 9 is a wireframe perspective view of the first embodiment of the present invention.

FIG. 10 is a perspective view of the second embodiment of the present invention;

FIG. 11 is a front view thereof;

FIG. 12 is a right side view thereof;

FIG. 13 is a rear view thereof.

FIG. 14 is a wireframe perspective view of the second embodiment of the present invention.

FIG. 15 is a front view of the first embodiment of the present invention with section cuts designated on the invention.

FIG. 16 is a right side section view of the first embodiment of the present invention depicting how air flows through the present invention. FIG. 17 is a top section view also showing how air flows through the device.

FIG. 18 is a front view of the second embodiment of the present invention with section cuts designated on the invention.

FIG. 19 is a right side section cut of the present invention depicting how air flows through the present invention.

FIG. 20 is a top section view showing how air flows through the present invention. FIG. 21 is a flow diagram of showing how the present invention helps to prevent vortex shedding.

DETAIL DESCRIPTIONS OF THE INVENTION

All illustrations of the drawings are for the purpose of describing selected versions of the present invention and are not intended to limit the scope of the present invention.

The present invention is a low drag low noise automobile mirror using jet flow control comprising both a first embodiment and a second embodiment. The first embodiment of the present invention comprises an outer body, an inner body, and a plurality of connection fins. In reference to FIG. 5, the outer body comprises a generally rectangular or elliptic base which is lofted into a generally rectangular or elliptic front. This gives the outer body a streamlined and aerodynamic shape which is desirable for the present invention. The outer body is mostly hollow with both the rectangular or elliptic base and rectangular or elliptic front being completely open such that air may flow through. The outer body is also hollow so that the inner body can be placed within the outer body. It is important to note that the shape of the base and the front of the outer body may be altered without altering the functionality of the present invention so long as the shape of the inner body is also changed to correspond with the outer body shape. For example, the outer body may comprise a elliptic base and a rectangular front and still function properly. It is important to note however that the front of the outer body must have smaller area than the base area such the outer body maintains the streamlined aerodynamic shape that is important to the effectiveness of the present invention. The purpose of the outer body is to fit over the inner body such that there is a small gap between the outer body and the inner body as can be seen in FIG. 8 and FIG. 9. The gap between the outer body and the inner body is a converging channel through reduction of channel area, accelerates and redirects the airflow to form a virtual trailing edge by the outlet jet downstream of the mirror surface to remove base vortex shedding and accomplish a reduction in drag and noise.

The inner body, as can be seen in FIG. 9, FIG. 16, and FIG 17 is formed to create the inner duct (e.g. generally conical or non-body of revolution in shape), and serves to help direct the airflow that enters the present invention through the front of the outer body. The inner body also comprises the mirror which is mounted to the rear surface of the inner body. The mirror is important to allow the present invention to retain functionality as a rear view mirror while also minimizing the effects of the base flow to reduce noise and drag. The inner body is entirely enclosed by the outer body except for the front and the rear of the inner body. As illustrated in FIG. 16 and 17 based on the cross section cut shown in FIG. 15, the front of the inner body protrudes out the front of the outer body and begin with small area of substantially tip shape. The area of the inner body gradually increases after the inlet tip to form a converging duct with the outer body. The duct is to introduce the flow from the front, accelerate and direct the flow to exit at the outlet at certain angle Alpha between zero and 45deg. The angle Alpha is defined as the angle between freestream direction (mostly horizontal) and exit jet velocity direction. Since the duct must have a converging shape, the desirable area ratio between the inlet and outlet is from 1.1 to 8.

The goal of the flow jet at the exit is to create a smooth virtual trailing edge as is displayed in FIG. 21. This smooth trailing edge prevents vortex shedding as well as increasing base pressure. By reducing vortex shedding and increasing base pressure, the noise and drag produced by the present invention is much lower than what is produced by a regular automobile rear view mirror. The exact angle and velocity at which the flow jet leaves the outlet may vary based upon the exact size and shape of the inlet and the outlet, as well as the size and shape of the outer body and the inner body, all of which is subject to potential change within the scope of the present invention. The optimum exit angle and velocity for the jet of air is not yet determined, and it is understood that the size and shape of the components of the present invention may be modified within the scope of the present invention in the interest of obtaining the optimum exit angle and velocity which results in the greatest reduction in both noise and drag.

The outer body and the inner body are connected to one another via the plurality of connection fins as can be seen in FIG. 8 and FIG. 9. The positioning of the plurality of connection fins may vary drastically, however as seen in the figures, the plurality of connection fins are located at the corners near the rear of the present invention in the preferred embodiment. It is important that the plurality of connection fins be as thin as possible such that they have minimal impact upon the shape and direction of the airflow that travels through the interior of the present invention. Of course, the exact number of connection fins, the shape, and the positioning of the plurality of connection fins may vary wildly in the final production of the present invention so long as the outer body and the inner body are physically connected in some way.

The second embodiment of the present invention works on the same principles as the first embodiment of the present invention and possesses all of the same components with the addition of one new component. In reference to FIG. 14, the new component is a central flow tube. The central flow tube is a circular or any other shape hole which traverses through the inner body from front to rear. The central flow tube has only one inlet and one outlet however, it is contemplated that the central flow tube could have a plurality of outlets distributed in a grid format. This configuration may be ideal to help reduce obstruction of the mirror as having one outlet for the central flow tube requires there to be a fairly large hole in the mirror as seen in FIG. 13. Having a plurality of smaller holes in the mirror may be less obstructive than having one larger hole. The purpose of the central flow tube is to allow air flow go through the center of the present invention. FIG. 10 is the external view of the second embodiment of the present invention. FIG. 11 and FIG. 13 are the view from front, side and back of the second embodiment of the present invention. A diagram depicting the airflow through the second embodiment of the present invention can be seen in FIG. 19 and FIG. 20 based on the cross section cut shown in FIG. 18. Allowing air to flow through the center of the present invention reduces the stagnation pressure at the front of the present invention and increases the base pressure in the mirror surface region. Reducing the stagnation pressure and increasing the base pressure causes a reduction in the pressure differential found when comparing the air in front of the present invention to the air behind the present invention. With the pressure differential between the front and the rear of the present invention reduced, the magnitude of pressure drag force that the present invention is subjected to is also reduced. Using the present invention on the motor vehicle as opposed to regular automobile side mirrors may have the effect of increasing fuel efficiency as the present invention generates much less drag than regular automobile side mirrors. The second embodiment of the present invention also maintains same effect as the first embodiment of the present invention, acting to reduce the level of drag and noise generated by the side view mirrors when the motor vehicle is in motion.

Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as herein described. Even though this invention is applied to air, it also equally applies to other fluids.