Radiators

The radiators are modeled in the app as a porous media. The volume of the radiator is represented by two surfaces and a frame. The frame represents the perimeter of the actual radiator core. The frame geometry is included in the engine or body geometry type and not the radiator geometry type. Two surfaces placed on the up and down stream side of the core matrix and these are the only surfaces that make up the radiator geometry type. The radiator type can have multiple files if there is more than one radiator in the vehicle but each file should have both surfaces inside it.

Below are some considerations when creating the radiator geometry

• Make sure the front and back surfaces are parallel.
• Both surfaces should have the same surface area.
• Surfaces should seal with walls they are against to ensure the fluid zone can’t leak-a leak will cause the porous zones to be omitted or the whole defined as a porous zone.

Flow Resistance Modeling

The pressure drop through the radiator is modeled using the Darcy-Weisbach equation approach to model the flow through a porous media.

The coefficients for the equations were determined from the pressure drop versus velocity curve from a representative racing radiator core. For this application, this resistance is fixed and cannot be changed by the user. The method of implementing the porosity is done per unit thickness so the radiator faces should be the actual thickness of the geometry in the aircraft. The pressure drop versus velocity curve used in the app is shown below.

In order for the solver to identify the volume of cells that will represent the radiator the ‘inside point’, attribute needs to be assigned to the geometry. The point should be in meters. This attribute will be defined for each radiator geometry file you upload. It should be a point that lies in between the two planes that represent the up and downstream face of the radiator. This point identifies where in the computational mesh the porosity properties will be defined.

Radiators straighten the flow that is passing through them so this property must be simulated as well. The radiator’s flow straightening property is modeled in the simulation through the definition of a normal and parallel vector. These are entered in the attribute region for the radiator geometry and need to be unit vectors that are space delimited. The normal vector represents the dominant flow direction through the radiator core (normal to the radiator face). The parallel vector is a direction that is parallel to the face of the core. These vectors are used to define which direction the flow will travel through the radiator. The normal vector direction will be given a lower resistance than the parallel direction to force the flow to travel the correct direction through the core.