k-Wave Toolbox |

## Setting An Initial Pressure Gradient Example

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Overview Defining the source properties

### Overview

This example demonstrates how to set an initial pressure gradient using `kspaceSecondOrder`. It builds on the Comparison Of Modelling Functions Example.

- open the file in the MATLAB Editor
- run the file in MATLAB

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### Defining the source properties

The function `kspaceSecondOrder` allows initial conditions for both the initial pressure and its temporal gradient to be explicitly defined. The initial conditions are defined as a matrix of arbitrary numeric values over the medium discretisation given by the k-space grid. The initial pressure is assigned to `source.p0`, while the initial pressure gradient is assigned to `source.dp0dt`.

In this example, `makeDisc` is used to create an initial source distribution of two small discs with different diameters. This is first assigned to the `p0` field of the `source` structure, then to the `dp0dt` field, and then to both fields. The optional input `'MeshPlot'` is set to `true` to allow a 3D visualisation of the pressure field. If `'PlotFrames'` is set to `true` the individual frames are spawned in new figures. A plot of the pressure field at two different values of t is shown below.

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© 2009, 2010, 2011 Bradley Treeby and Ben Cox.