AU2014259581B2

AU2014259581B2 - A method for reducing aerodynamic forces associated with turbulent flow or drag on a moving vehicle

Info

Publication number: AU2014259581B2
Application number: AU2014259581A
Authority: AU
Inventors: Todd James Andrews
Original assignee: Andrews Todd
Current assignee: Andrews Todd
Priority date: 2014-11-09
Filing date: 2014-11-09
Publication date: 2016-10-06
Anticipated expiration: 2034-11-09
Also published as: AU2014259581A1

Abstract

Abstract The purpose of this paper is to present ideas for minimising the drag forces on the rear of moving objects such as vehicles, planes, trains and trucks etc. This paper also presents the theory of which these ideas are based, basic findings from initial modelling and further formulas and ideas for modelling the theory at a higher detail. Ideas put forth in this paper were based on fluid dynamic principles. These principles included laminar flow of pipes and the fact that water undergoes natural changes of pressure through a pipe called laminar flow. Basically it is assumed that using a flow with extra velocities and a 'structured' design like that associated with laminar flow, will be drawn to the low pressures and 'interrupt' turbulent flow and in turn increase the air pressures at these locations. This in turn will lead to the reduction of drag forces.

Description

DESCRIPTION

Aero-dynamics is the ability for an object to advance with as little drag force as possible. This patent describes a method by which to reduce the low pressures and resultant forces, at the rear of a moving object due to flow separation, and thereby reducing the turbulent flow or eddying and aerodynamic drag.

Laminar flow works under the principle of a bounded flow where the boundary layer growth of the passing viscous material becomes fully developed over a minimum critical length based on the surface roughness of the pipe and the viscosity of the fluid. In turn the central flow of the pipe is quicker than the outer layer flows of the pipe. Over a minimum distance, before pipe loses occur, the central flows are quicker than the initial flows of the liquid into the pipe due to this layer separation. A method to reduce the drag forces on a moving object such as a vehicle is to provide pipes on the sides of the vehicle at the end of the vehicle. The pipes would be straight for a minimum critical length for fully developed laminar flow to develop. Airflow passing the moving vehicle would be forced through the pipes and become laminar, this would be the case for the air exiting the pipe as well. Similarly, the resulting air leaving the pipe would have a subsequent velocity in the central discrete layers relative to the speed of the air passing the vehicle. This air with a velocity would need to dissipate and would be naturally attracted in the direction of the low pressures caused by flow separation and eddying. This would result in the low pressures equalising and in turn naturally lower the forces associated. Please refer to the attached figures 1 and 2 for a schematic representation.

This method could also be reciprocated with the forces associated with drag or turbulent flow of aircraft motion. Whereby through laminar induction, the high flow laminar particles would equalise the drag forces.

For water, the super critical pipe flow occurs at a minimum distance of 110 x the pipe diameter which is relative to the fluid viscosity. We can assume that the fractional difference for water to air based on viscosity would be 0.018. This would calculate a minimum pipe length for laminar flow of air to be 2 to 4 times the internal diameter of the pipe. This however is a assumption and further testing is required. A practical experiment has supported the ideas put forth in this paper. Using light debris in the tray of a utility vehicle, it was observed that: • prior to the installation of hydraulic pipes the debris in the tray was eddying behind the vehicle cabin. • After installation the debris disbursed from behind the cabin and was blown out of the tray altogether. • This was done early in the morning in still conditions to limit other possible factors for interfering with the experiment.

On a whole results seem to be most promising with a pipe on both sides of the car simultaneously. Pipe length seems to be effective at 3-4 times the pipe diameter, though results are noticeably stronger with longer length pipes such as 6 time the pipe diameter.

With this in mind, the aim is to further test the results in a wind tunnel, while measuring the differences in pressure on the rear of the vehicle with and without the laminar pipework. This would be ideal as a wind tunnel limits the external factors of ambient conditions and would produce stronger testing results.

Investigations will need to be conducted to find an exact harmony for the fully developed pipe flow of air. At this time, different humidity's could also be incorporated into the testing. A study could then be based on the collisions of opposing flow types and could then be investigated with respect to modern car shapes with respect to position, size and quantity.

In summary, the principal of this method to reduce aerodynamic forces of turbulent flow or drag on a moving vehicle, is that the inherent velocity of the particles exiting the pipe(s) as described above, would need to dissipate and be attracted to the resulting low pressures render them neutral pressures and in turn reduce the aerodynamic forces associated. This could in turn produce better fuel economy and less wear and tear on the vehicle.

Claims

CLAIMS What is claimed is:

1. A method to reduce the aerodynamic forces associated with drag or turbulent flow on a moving vehicle by providing straight circular pipe(s)with a uniform diameter and no internal componentry, attached to the side(s) of a vehicle parallel to the standard X-axis will create fully developed laminar flow of the air being naturally forced through the pipe resulting in laminar flow exiting the pipe where the central layers have a velocity greater than the external air outside the pipe that would in turn need to dissipate and would be naturally attracted to the drag behind the vehicle and neutralise the pressures thereby reducing these resultant forces.
2. The method according to claim 1, wherein the minimum length to create fully developed laminar flow within the pipe is based on the fluid viscosity and pipe roughness.
3. The method according to claim 1, wherein the pipe is/are positioned so that the rear end of the pipe is positioned before the rear of the vehicle for reducing drag pressures.