MIT Java Pflow

User Guide for version 1.0 (rev 2.2)

1. Introduction
    1.1 Requirements
2. User Interface
    2.1 Principles
    2.2 Overview
3. Functionality
    3.1 Singularities
       3.1.1 Free Stream
       3.1.2 2D Source
       3.1.3 2D Vortex
       3.1.4 2D Dipole
       3.1.5 Corner Flow
    3.2 Visualization Options
       3.2.1 Point Evaluation
       3.2.2 Vector Field
       3.2.3 Grid and Grid Scale
       3.2.4 Plot Stream Lines
       3.2.5 Pressure Coefficient
    3.3 Other Options
       3.3.1 Zoom
       3.3.2 Reset
       3.3.3 Context Menu
    3.4 Adding Singularities
       3.4.1 Notes
4. Credits

Introduction

MIT Java Pflow is a Java applet that computes and visualizes the potential flow function inputed by the user. The potential flow field is built as a superposition of basic flow singularities.

Requirements

MIT Java Pflow was implemented in standard Java under Sun Microsystems 1.4.1 JDK. Successfully running it requires at a minimum a Web Browser and 1.4.1 Java Virtual Machine plugin correctly installed. A three-button mouse is also strongly recommended to take full advantage of the GUI functionality (an operating system emulating third-button click such as Linux should also work).

User Interface

Mit Java Pflow fully utilizes the input capabilities provided by point-and-click devices. Nothwithstanding, the interface can also be driven via keyboard input and there are viable tab-navigation paths in the user interface.

Principles

Left click is used for the primary input of the visualization options currently active. It also provides coordinates to the facility used to input the basic flow singularities.

Right click provides a secondary (optional) input point facility, used to input as many secondary points as might be required by the selected visualization options. Not all visualization options need or use right-click secondary input points.

Center click provides a way to the user to clear all the active visualization options, Note that this leaves all the visualization options not active at the time completely unaffected, so the user can selectively clear just the content of one visualization by deactivating all other visualization options, center-clicking to clear only the option(s) remained active and then re-activate the other options, which will have reatined their previous state.

Overview

The MIT Java Pflow GUI is composed of three main sections: a display panel at the top, a visualization/display option pane below it, and an area dedicated to the insertion of new basic flow singularities at the bottom.

The display panel is sensitive to all three types of clicking and it responds according to the visualization options which are activated at the time of the click. The display area is a four-quadrant display within the domains described by the (x,y) pairs at the four corners of it. The scale of the display area (and corresponding domains) are affected by the zoom ratio selected in the ZOOM combo box in the option pane, which effectively represents the ratio of display area pixels to the effective units of the coordinate system.

left-clicking in the display panel updates the x,y values in the add singularities area to match the location of the user's click:

similrly, hovering on the display panel results in the current mouse coordinates being displayed in the left of the status bar located at the applet's bottom.

Functionality

The applet provides three distinct kinds of functionality: insertion of the basic singularities, definition and handling of the visualization options, and management of the input values stored in memory.

Singularities

Currently the system supports five types of basic singularities and their respective subtypes:

Free Stream

    Free Stream is defined by a (strength, orientation) pair which is printed to the screen in that order. Orientation is measured in radians, counterclockwise from three o'clock. The Free Stream icon is also displaying the orientation angle by pointing in its direction.

   2D Source

    The 2D Source singularity is defined by a location and a strength. The latter one is printed near the icon representing the singularity for the user's convenience. A 2d Source is displayed as a filled square, while a 2d Sink is represented by a hollow square.

   2D Vortex

    A 2d vortex is similarly defined by a strength (circulation) and a location. A reminder of the strength of the vortex is placed next to the icon for the user's convenience. Akin to the 2D Source representation, the 2D Vortex icon (a circle) is hollow if the strength value is less than zero.

   2D Dipole

    A 2D Dipole is defined by its strength, orientation and coordinates, the first two of which the user is reminded of next to the icon marking the dipole's location. Similarly to the previous two singularities, a negative value in strength is plotted with a hollow icon (a diamond in this case).

   Corner Flow

    Corner Flow is defined by its location and the orientation parameter, which can assume only a specific set of values. Corner flow is represented by a rectangular bracket whose orientation is independent the orientation parameter.
Visualization Options

    Point Evaluation

    The point evaluation visualization option displays a vector representing the strength and direction of the velocity field at the point of a user's click. Additional information is provided numerically in the form of the following pairs: (x,y), (u,v). p, where p stands for the pressure at the given point ((1- (v^2 + u^2))/ U) where U is the Free Stream strenght (or 1 if no Free Stream is present).

    The current set of Point Evaluations can be cleared by clicking the middle mouse button while the option is enabled.

    Vector Field

    The Vector Field visualization option plots the vectors composing the velocity field in the same way Point Evaluation does, except that it does not provide the additional numerical information that Point evaluation includes. Point Evaluation and Vector Field are mutually exclusive, meaning that activating one option will automatically disable the other if that was selected at that time. State is preserved, so it is possible to revert to the previous selection by selecting it once again.

    The vector field is plotted at the intersection points of the grid, and its density can be manipulated by using the Grid Size scroller.

    Grid and GridScale

    The Grid checkbox enables a reference grid which is used, among other things, to determine the plotting points of the vector field. The Grid Scale scroller controls the density of the grid. The Grid Scale scroller will not be enabled unless the grid is enabled as well.

    Plot Stream Lines

    The Plot Stream Lines visualization option initiates tracing of a streamline starting at a point given by the user with a left-click on the display panel. This is done in two steps from the initial point, and can take up to 10,000 iterations to complete.

    The current set of Stream lines can be cleared by clicking the middle mouse button while the option is enabled.

    Pressure Coefficient

    The Pressure Coefficient visualization option initiates tracing of a streamline in exactly the same way the Plot Stream Lines option. If the user whishes to visualize a pressure contour on this streamline, she must select two points on the streamline between which the pressure contour will be plotted - this is done with the secundary input button, which is the right mouse button.

    Please note that you can select endpoints of the pressure contour only on the last streamline you traced.

    The current set of Stream lines and any pressure contour associated with them can be cleared by clicking the middle mouse button while the option is enabled.

Other Options

    Zoom

    Zoom provides a number of levels of magnification on the display panel. Zoom is always performed with respect to the origin of the coordinate axis in the current version of MIT Java Pflow.

    Information on the endpoints of the domain currently being displayed by the graphic panel is provided in the four corners of said panel in the form of (x,y) pairs corresponding to the extremities of the drawing canvas.

    Reset

    The Reset button will clear the applet state in its entirety, removing all streamlines, point evaluations, pressure contours or singularities that the user might have inputted. This is different from using the middle mouse button as the latter only clears the currently active visualization options and never affects the singularities themselves.

    Context Menu

    The secondary mouse button triggers a context munu in the option pane. When the user
right-clicks the following choices are presented:

The first selection brings up this help file in a new browser window, while the second one brings up the Authorship/copyright dialog.

Adding Singularities

Notes

None at this time.

Credits