Reducing Vehicle Drag by Actively Promoting Laminar Airflow

November 27, 2008

Reducing Vehicle Drag by Actively Promoting Laminar Airflow
~James Dunn

One of the ways to provide Green technologies is to provide means for saving and conserving energy. One of the reasons why we don’t have cars that get over 100 miles per gallon is that the air must be pushed out of the way as a vehicle moves. The heat produced translates to more fuel used. Turbulent or Burbling air flow tosses air violently about causing the creation of significant heat. Laminar air flow minimizes the disturbance of air so that friction is minimized.

Explanation of Laminar and Burbling (turbulent) Air Flow

Cars typically have areas of drag that are necessary for the operation of a vehicle, like the radiator. Some air must flow through the radiator to cool the engine. This results in air flow burbling that contributes to total vehicle drag.

Vehicles also have body part transitions that cause burbling of air passing across the transitions.

Potentially in these areas, the control of air flow can help to provide consistent laminar air flow over the body of the vehicle. Something like blowing into a flute, as your finger covers the hole you hear a change in pitch quality. The back pressure can help control the boundary layer and contribute to lower drag of the vehicle under dynamically changing environmental conditions.

Areas where this boundary layer might be beneficially controlled would be the front bumper/grill to hood interface, hood/windshield interface, wheel wells, roof to back window interface, back window to trunk lid interface, trunk lid to bumper interface.

Instead of a front grille, NASA vents (V shaped vent port that allows air to pass through without significantly disturbing laminar air flow) would pull air in to cool the radiator; thereby establishing laminar air flow across the body. For instance, a diesel truck might have the radiator lay back at 45 degrees and have NASA vents to promote laminar air flow and protect the radiator from debris. The windshield could lay back and flow smoothly over and around the cab.

The transition between each surface element could monitor air pressure and/or other physical variable and operate a vent or air pump/jets to promote a stable layer of air density for a given set of environmental conditions (humidity, temp, air pressure, …). At aerodynamic surface transitions the pressure is greater, or less than, the average surface pressure and the resulting airflow could provide spin of a turbine to produce a very small amount of electrical power; or running of the turbine could cause aerodynamic qualities to allow the vehicle to slip through the air with less power. A computer would determine the mode of most efficient energy usage.

Care must be taken to ensure the vehicle body does not become a flying wing and loft the vehicle off of the roadway. Ground effect can be used in conjunction with low pressure zones to help suck the vehicle down onto the roadway.

Dynamic skirting could conceivably maintain a fixed distance from the roadway to create a large low-pressure zone under the vehicle to increase vehicle stability; controllably sucking the vehicle to the roadway.

The complexity of such a system would require an aerodynamics engineer to determine the configuration of the body, NASA vents, and turbine units needed to promote laminar flow. NASA vents could be used where air intake is needed. Surface bumps could be used to break up large burble vortex into small burble so that the air can transition more quickly back into laminar air flow. Small holes with an air supply in the surface can lead transitions to virtually shape aerodynamic surfaces to promote smooth transitions.

The turbine/laminar flow configuration could reduce vehicle total drag and potentially produce a small amount of power in burble areas of air flow.

However, if the extra weight of vectoring vents and ducts is excessive, the additional weight and impeding structures under the hood, would contribute to making this solution impractical. Costly, cumbersome, and power consuming instead of power saving.

However, a vehicle traveling 150 mph straight and level that has 95% of its’ surface in laminar air flow can travel at the same speed with considerably less horsepower as a vehicle with 50% of its’ surface in laminar air flow; even if the vehicle weighs an extra 200 pounds. This is proven in aircraft like the Rutan Varieze.

Does 150 mph seem fast for driving? With the future of autopilot for automobiles this is a realistic expectation. How fast could you safely drive if you could anticipate every obstacle long before arriving at the obstacle? This is the future of autopilot technology. Because the location of everything is known and controlled, the cruising speeds of vehicles can substantially be increased.


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