How to model multiple passages with a single thermal stream

This example shows how to model multiple holes with a single cylindrical stream.

This modeling approach is effective when multiple holes are circumferentially distributed in a circular pattern around the axis of rotation, and oriented in the same cylindrical direction. In this case, you can represent the flow through all of the holes using a single cylindrical thermal stream.

Using one stream for multiple holes instead of one stream per hole removes the limit of 10 streams that can be mixed using the MIX and MMIX thermal-flow functions.

Note:
If holes are not aligned in the same cylindrical direction or do not share a similar orientation, use one cylindrical stream per hole.

Details

To model multiple holes using a single cylindrical stream, use the following guidelines:

  1. Create a thermal stream of type One-Sided Stream on Faces (Cylindrical Components).
  2. Select the set of holes that are all circumferentially distributed in a circular pattern around the axis of rotation.
    Circular component with evenly spaced holes circumferentially distributed in a circular pattern around the axis of rotation
  3. Set the radial, circumferential, and axial components of the stream flow direction with respect to the selected cylindrical CSYS. This means that the global cyclic axis of your model is used as the cylindrical axis, typically the engine centerline. You specify the direction of the thermal stream using three components as shown in the following image.
    The dialog box showing cylindrical coordinate inputs: radial set to 0.5, circumferential to 0, and axial to 0.5 under a Global Cyclic Analysis system.
  4. Specify thermal stream conditions such as the mass flow, initial temperature, and absolute pressure. If the holes are identical and evenly spaced, the solver distributes the flow across the entire cylindrical duct.
    Note:

    You must specify the total mass flow for the entire circumferential region, not just the flow through a single hole.

  5. Specify the heat transfer coefficient (HTC) applied to the entire annular flow path. A cylindrical thermal stream models one continuous 1D flow domain, an annular duct, wrapping around the geometry. The thermal solver couples this duct to the selected circumferential surface area.

    • HTC is applied to the total wetted area.

    • HTC governs heat transfer between the annular duct and all surfaces along that duct.

    • HTC is not subdivided by geometric features such as holes, slots, or ports.

  6. After solving, always review the solver-created duct geometry, the temperature distribution, and the thermal coupling to the solid to ensure that they meet your expectations and accurately represent the intended flow behavior.
    Top image shows a circular model with a temperature distribution, the bottom image shows temperature distribution for the radial ducts.
  7. In post-processing, under the Groups node→Thermal Stream - Nodal, display thermal stream groups to graphically identify whether the created ducts and solid elements are correctly connected thermally.
    Temperature distribution shown along each 1D duct and its adjoining solid elements.