To create curved walls in PyroSim, you can use any of the following techniques:

In all of the following examples, we will use a background image as a pattern to draw against. While this is not required, it makes creating curved surfaces much easier and one of the strengths of PyroSim is that it allows you to sketch geometry directly on top of building design images. The background image we will be using is shown in Figure 9.1.

Figure 9.1. Background image used for all curved wall examples

For simplicity, we will assume that horizontal distance across the entire image is 50 feet, and we will place the origin of the model at the lower-left corner of the room shown in the image. The brightness of the image will be set to 50%. The Configure Background Image dialog shown in Figure 9.2 illustrates these settings.

Figure 9.2. Background image settings for curved wall examples

Using the Wall Tool

To create a curved wall section from wall segments, you can follow these steps:

1. Click the 2D View tab, and select the Draw a Wall tool.

2. Turn off grid snapping. In the View menu, click to clear the Snap to Grid option.

3. Position the pointer at the beginning of the curve where you want to place the first wall segment.

4. Click and drag the mouse to extend the wall segment across a portion of the curve. Release when you have completed the first segment. Shorter segments will produce smoother curves.

5. Create the next segment using the end point of the first. You can create as many segments as you need in this way until the curve is completed.

This is the fastest way to create smooth curves in PyroSim. PyroSim will convert the curved walls to blocks before running the FDS simulation. While smaller segments will make the wall look better in PyroSim, placement of obstructions generated for FDS depends on the resolution of your mesh. Three different versions of a curved wall created with this technique are shown in Figure 9.3.

Figure 9.3. A curved wall drawn with three different segment lengths

Using extremely short line segments will probably not be of any benefit unless you also use very small mesh cells.

Using the Block Tool

To create a curved wall section from blocks, you can follow these steps:

1. Create a mesh. This example uses a 50.0 ft x 50.0 ft mesh with 1 ft mesh cells.

2. Click the 2D View tab, and select the Draw a Block tool.

3. Turn grid snapping on. If snapping is off: in the View menu, click Snap to Grid.

4. Click each cell along the curved wall to place the necessary blocks.

This technique forces you to convert the curve to blocks manually, but the advantage is you know exactly what geometry will be generated for FDS. If you have a high resolution mesh, it may be useful to drag the mouse and "paint" the curve rather than clicking individual blocks. The example curved wall is shown in Figure 9.4.

Figure 9.4. A curved wall drawn using individual blocks

Rotating an Object

To create curved objects using the rotation technique, you must place an initial segment, then perform a rotate-copy operation about the center point of your desired curve. This process is illustrated in the following steps:

1. Click the 2D View tab, and select the Draw a Wall tool.

2. Turn off grid snapping. If snapping is on: in the View menu, click Snap to Grid.

3. Create an initial wall segment somewhere on the curve.

4. In the Model menu, click Rotate...

5. Select the Copy mode.

6. Specify the necessary parameters for the rotation operation. In this example, the Number of Copies is 15, the Angle is 6.0 degrees, and the Base Point is: x=32.0 feet, y=16.5 feet.

7. Click Preview to verify that the settings are correct, then click OK.

The curve for this example is shown in Figure 9.5.

Figure 9.5. A curved wall drawn using the rotate technique

If we would have created 60 copies instead of 15 this procedure would have created a cylinder. While complicated, the rotation approach is the most effective at creating complex symmetrical geometry.

You can create trusses by drawing a single truss out of blocks, then replicating that truss as many times as needed. The following steps show how to create the trusses for an example roof.

The trusses created in this example are shown in Figure 9.6.

Figure 9.6. Trusses created using the block tool and the replicate function

You can quickly add a roof to the model using the New Triangle tool. The following steps show how to add a roof to the previous truss example using triangles.

Notice that the coordinates for each roof section were given in counter-clockwise order (if you are looking down from above the model). The ordering of the coordinates determines the direction in which the width of the triangle extends. For triangle width, PyroSim uses a left hand rule. This means the width of each roof section will extend upward. The result of adding all four roof triangles is shown in Figure 9.7.

Figure 9.7. A roof created with the triangle tool

You can create simple stairways by placing the initial stair, then using the translate-copy operation. This section will present a simple example to illustrate the approach.

We will create a 10 step stairway. Each step will have a 7 inch rise (0.58 feet), and a 10 inch (0.83 feet) run. The stairway itself will be 24 inches (2.0 feet) wide. To keep things as simple as possible, we will construct the stairway in an empty model.

The stairway generated in this example is shown in Figure 9.8.

Figure 9.8. A stairway created with the replicate tool