# Geometry¶

## Starting Ambiens¶

To open a previously created New Generation Ambiens model, choose open from the file menu or press ctrl and “O”. Bitmaps can be imported so the user can trace around them. This is done by selecting “bitmap” from the file menu, selecting the bitmap and then clicking on the “open” button. It is recommended that the bitmap is saved as 256 colours. The size and the position of the bitmap can be altered by selecting “adjust origin” from the file menu. This will bring up a dialog box with the following parameters:

• Origin X: the horizontal distance between the top left hand corner of the bitmap and the top left hand corner of the grid. The distance is measured in pixels.

• Origin Y: the vertical distance between the top left hand corner of the bitmap and the top left hand corner of the grid. The distance is measured in pixels.

• Factor: the value used for scaling the bitmap.

## Setting the Scale¶

Right clicking anywhere on the grid brings up the cell parameters dialog box. It has the following parameters:

• Cell dimension: the size of a single cell. It is measured in metres. By default this value is 0.1. This means each square represents an area of 0.1m by 0.1m.

• Cell X: the number of cells in the grid in the horizontal direction

• Cell Y: the number of cells in the grid in the vertical direction.

The cell x and y are measured from the origin, which is in the top left corner of the grid. The cell parameters can be altered at any time.

## Drawing the Outline¶

To start to draw the section, left click the “Add vertex” button then move the cursor to the location on the grid for the first point. Left click to locate the point then move the cursor to the location on the grid for the second point. A left click will locate the point and draw a straight line between the two points. To draw the next line simply move the cursor to the required location for the next point and left click. A second line will be drawn between the two points. The process is continued until all the necessary points have been located. When the final point has been input left click the “add vertex” button. This will stop the input of further points and draw a line between the last point and the first point, thus completing the section.

There are some important rules when inserting points:

• A Drawing created in Ambiens represents a 1 metre deep vertical cross-section through a building.

• The section can be entered in a clockwise or anti-clockwise direction.

• No line segments may cross ( i.e. intersect each other)

## Inserting Points¶

Whilst the general shape of the section is complete more detail can be added. These details will include inlets and outlet for air to flow through. The first stage of adding these features is to insert additional points. This is done by clicking on the “insert vertex” button and then clicking on the cells which represent the boundaries.

## Display Options¶

There are display options that can help with the drawing of the model. They are zoom in, zoom out and fit all, which will do a best fit view of the model. There is also a feature called the over view window. To use this feature, select “overview window” from the view menu. This will bring up a small window which displays the entirety of the model. The window also contains a dotted rectangle which shows the area that is currently being displayed in the main window. Moving this rectangle will change the view shown in the main window. To move the rectangle, left click on it, hold down the left mouse button, move the cursor to the new position and then release the mouse button.

Features, such as inlets and outlets can be allocated to each segment. The additional features can only be done when Ambiens is in “select” mode. To put Ambiens into “select” mode, click the “select” button. To change a segment into an inlet, left click on it and then right click to bring up the pop-up menu and select inlet from it.

Here are some important rules for locating an inlet or outlet:

• Inlets and outlets must be horizontal or vertical.

• An inlet or outlet must be followed immediately by a segment of wall drawn in the same horizontal or vertical direction (the segment that follows only needs to be one cell long if necessary).

• A diagonal segment of wall must not start from the end of an inlet or outlet.

• If the model contains at least one inlet it must contain at least one outlet and vice-versa.

The colour of the wall can be changed so to represent a window or radiator. This is done by left clicking on the segment, then right clicking on it and selecting a new colour from the pop-menu. Changing the colour is only done for visual purposes and does not affect the results.

## Deleting and Moving Points¶

The first stage of moving points is to click on the “move” button. Whilst this button is depressed one or more points can be moved. Click on the point, hold down the mouse button, move the cursor to the new position and then release the mouse button.

To delete a point, click on the “delete” button then on each of the points that are to be removed. When a point is deleted, the points either side of the deleted point will become connected by a segment. If the building contains only three points, then those points cannot be deleted.

## Gains¶

Regions within the section that have heat gains (or a cooling effect) can be input as rectangles as small as a single cell. To insert a gain click on the “add gain” button Then click on the grid, hold down the mouse button, drag the cursor and then release the mouse button. To delete a gain, click on the “delete” button then on the gain. To move a gain, click on the move button and then drag and drop the gain to a new position. To re-size a gain, click on the “Resize” button then click on the gain, hold down the mouse button, move the cursor and then release the mouse button.

Here are some important rules for inserting gains.

• Gains should not overlap each other.

• Gains should not cross the boundary or lay on the boundary.

• In general avoid putting gains in cells adjacent to the boundary. If a gain is placed adjacent to a boundary any radiant heat component will not be included for the region cells next to the boundary.