What is Fluid: Definition and 1000 Discussions

FLUID (Fast Light User Interface Designer) is a graphical editor and GUI builder that is used to produce FLTK source code. FLUID edits and saves its state in text .fl files, which can be edited in a text editor for finer control over display and behavior.After designing the application, FLUID compiles the .fl file into a .cxx file, which defines all the objects from the .fl file, and an .h file, which declares all the global ones. FLUID also supports localization of label strings using message files and the GNU gettext or POSIX catgets interfaces.

A simple program can be made by putting all non-interface code (including a main function) into the .fl file, thus making the .cxx file a single source file to compile. Most programs are more complex than this, so other .cxx files can be written that call the FLUID functions. These .cxx files must #include the .h file, or they can #include the .cxx file so it still appears to be a single source file.
Normally the FLUID file defines one or more functions or classes, which output C++ code. Each function defines one or more FLTK windows, and all the widgets that go inside those windows.
Widgets created by FLUID are "named", "complex named", or "unnamed". A named widget has a legal C++ variable identifier as its name (i.e. only alphanumeric and underscore), and is defined by a global variable or class member that will point at the widget after the function defining it is called. A complex named object has punctuation such as '.' or '->' or any other symbols in its name. In this case, FLUID assigns a pointer to the widget to the name, but does not attempt to declare it. This can be used to get the widgets into structures. An unnamed widget has a blank name and no pointer is stored.
Widgets may either call a named callback function that one writes in another source file, or one can supply a small piece of C++ source and FLUID will write a private callback function into the .cxx file.

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  1. squelch

    Pressure of a fluid contained in a steel container

    Homework Statement A steel container is completely filled with gasoline, and then sealed. The temperature is then increased 11 degrees C. If the bulk modulus of gasoline is 1.90 \times {10^9}Pa, find the increase in pressure of the gasoline if: (a) The expansion of the container is considered...
  2. SnakeDoc

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  3. M

    Verifying Stokes' Flow for Fluid Motion Around a Sphere

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  4. S

    Bernoulli's equation and fluid movement

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  5. T

    Magnetic field due to flowing charged fluid

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  6. Feodalherren

    Fluid Mechanics: viscous flow in pipes

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  7. M

    Modeling Deceleration of Object Towed in Water

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  8. ryanuser

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  9. U

    Hydrostatics on plane surface (basic fluid mechanic Q)

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  10. A

    Exploring Advective Acceleration in Fluid Mechanics

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  11. M

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  12. andyrk

    Direction of pressure in a Fluid

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  13. S

    Nozzle problem between subsonic and supersonic speed & nozzle area

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  14. AdityaDev

    How does the melting of ice affect the oil-water interface in a fluid system?

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  15. R

    Need help re: air pressure to fluid pressure

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  16. L

    What is the resultant force exerted by the sides of the glass on the water?

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  17. L

    Classical I need a fluid mechanics textbook

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  18. M

    Fluid mechanics~ Bulk modulus

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  19. B

    Molecular Modeling of Fluid Mechanics

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  20. A

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  21. Feodalherren

    Computational fluid dynamics: steady 2D flow

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  22. Feodalherren

    Fluid Dynamics: Conservation of momentum equation

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  23. Wyn

    Other Intr. Fluid Mech. for Physicists and Mathematicians by Pert

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  24. Saumya Kar

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    While the sound waves travel in a medium, let's say a fluid, what is the difference between fluid pressure and acoustic pressure ? Are these entities same?
  25. Q

    Problem of fluid -- Blocks, pulley, two fluids

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  26. Z

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  27. A

    Fluid dynamics question (Poiseuille)

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  28. A

    Calculation of the force exerted by a liquid

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  29. Q

    Fluid problem -- Piston moving in an oil-filled cylinder

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  30. A

    Pressure and normal stress in fluid mechanics

    Hi, everyone. I am learning fluid mechanics. One book says that for a infinitesimal fluid cell, surface force includes 1) the pressure, which is imposed by the outside fluids surrounding the concerned fluid cell 2) the shear and normal stress, which result in shear deformation and volume...
  31. Feodalherren

    Newtonian fluid mechanics: Navier-Stokes equation

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  32. L

    Do diabetics have sugary interstitial fluid?

    So my understanding is that capillaries leak out their blood plasma containing sugar and other nutrients insulin (when sugar present)near body cells, and this is what comprises interstitial fluid. But what if no insulin is present (Type 1 diabetes) or insulin creates no response (Type 2...
  33. Dennydont

    Velocity of fluid in venturi tube

    Homework Statement A venturi tube is a means of measuring fluid velocity. One particular device consists of a level, circular pipe of radius 5.7 cm which at one point narrows to a radius of 3.7 cm. An ideal, incompressible liquid flows through the tube and the pressure difference between the...
  34. L

    Fluid statics- pressure intensity and hydrostatic force

    Homework Statement a concrete dam, 20m in height, has a vertical upstream face. if the water level is coincident with the top of the dame, calculate and plot the pressure intensity at 4m intervals over a vertical and thus determine the total hydrostatic force acting per unit width. Show that...
  35. D

    Fluid mechanics: intuition about the 'convective' term

    Hi, I am doing an introductory course on fluid mechanics, and I'd like some intuition (that's why I'm posting on the engineering forums and not on the math forums, even if I'm studying for a degree in math) about the concept of the total derivative and, particularly, its convective component...
  36. T

    Fluid dynamics - find velocity of a particle in a vector fie

    Homework Statement Determine the speed of a fluid particle at the origin and at a point (1,-2,0) for each of the following velocity fields when t = 2s. All distances are in meters and t is in seconds. V = (x+2)i + xtj - zk m/s Homework Equations V x dr = 0 dV/dt = u(dV/dx) + v(dV/dy) +...
  37. T

    Pressure and velocity calculation for microchannel. pls help

    Me and my friends have been trying (b) for soooo long! we have gone to PhD students and some fluid dynamic doctors for held and they cannot figure this out. 1. Homework Statement 2) This question concerns the design of a ‘micro-chemostat’ device. E. coli exhibiting chemotaxis can swim up to...
  38. Feodalherren

    Fluid Mechanics: Hydrostatic Pressure on a gate with hinges

    Homework Statement Homework Equations Fluid Mechanics The Attempt at a Solution Lets start with the easy part: The pressure of the air is constant so the pressure will act as if it's a concentrated force on the center of gravity of the gate. F = PA = (10,000Pa)(.3)(.6)=1800N The moment...
  39. M

    Venturi, how does fluid go from low P tube to high P tube

    Homework Statement How does fluid move from low pressure area in a Venturi to a high pressure area, which is downstream from the Venturi. Homework EquationsThe Attempt at a Solution Not understanding the mechanism here, as I thought fluids only go from high pressure to low presure. Since the...
  40. Feodalherren

    Fluid Mechanics: Manometry - Fluid through a pipe

    Homework Statement Homework Equations Hydrostatic equation The Attempt at a Solution Call length from 2 to the Hg "h". Yhg = specific weight of Hg, from book = 846lbf/ft^3 Yw= water = 62.4 lbf / ft^3 Then P2 = P1 + Yw(5sin45 + h + .5) - Yhg(.5) - Yw(h) Then P2 - P1 = simplify and plug in...
  41. C

    Pressure change when volume changes for incompressible fluid

    Homework Statement Hi guys, My first post here, I hope someone can help me out with a quick fluid mechanics problem. I'm looking to calculate the pressure increase inside a closed tube full of water when the tube is crushed and therefore its volume reduced. The tube is filled completely...
  42. Feodalherren

    Fluid Mechanics: Rotating cylinder viscometer

    Homework Statement Homework Equations τ = μ (du/dy) The Attempt at a Solution For part B) dM = τr dA τ = μ (rΩ/Δr) ∫ (μrΩr2πr / Δr)dr = μR4πΩ / 2Δr pretty sure that's correct. I'm confused for part A though. I want to set it up as dM = τR dA = τR (2πRdL) and τ = μ (RΩ/L)...
  43. N

    Roman Inverted Siphons and Fluid Dynamics

    Homework Statement "Inverted siphons were used by the Romans to cross some valleys. If the height difference between the top of the valley and the bottom is 10 meters, the pressure in the pipe at the bottom of the valley will be ____. Homework Equations Bernoulli's Equation P1+(pv^2)/2 + pgh1...
  44. S

    Water Pressure in an Isolated System

    So I'm more into electricity, so fluids is not really a forte at all. But I have been thinking about this, and there must be some fundamental issue in the way that I view fluid pressure. Conditions: 1. I have a metal pipe, incompressible 2. There is water in the pipe, (incompressible? ...
  45. B

    Fluid Mechanics: velocity u for circular pipe

    Homework Statement For low-speed(laminar) , steady flow through a circular pipe, the velocity u varies with radius and takes what form? Please see this link for picture of the pipe...
  46. Feodalherren

    Fluid Mechanics: Cone-Plate viscometer

    Homework Statement Homework Equations Fluid Mechanics τ =μ (du/dy) The Attempt at a Solution I got far enough to write down dM = μ (Ωr/tanθ) dA from just substitutions, easy enough. I get confused when I'm solving for the differential surface area. I somehow need the dA for a cone. For...
  47. T

    Pressure Propagation through Fluid

    I have been searching for an explanation of how a change in pressure propagates thru a fluid to become isotropic. My question is that if the time scale measured is small enough ( much less than the distance divided speed of sound ) will we see the pressure change have an initial direction and...
  48. R

    Flow Rate in Horizontal Rectangular Channel: Solve Now

    Homework Statement In a horizontal rectangular open channel 20 m wide the water depth is 9 m. When a smooth hump 1.5 m high is introduced in the channel floor, a drop of 1 m is produced in the water surface. What is the flow rate, neglecting energy losses? It is proposed to place a pier at the...
  49. P

    What is the Acceleration of a Spherical Shell Filled with Fluid on an Incline?

    Homework Statement A spherical shell of mass M and radius R is completely filled with a frictionless fluid, also of mass M. It is released from rest, and then it rolls without slipping down an incline that makes an angle θ with the horizontal. What will be the acceleration of the shell down the...
  50. adoion

    Question about fluid expansion

    Hi, When a hot and dense fluid suddenly expands, how much can it cool down. Lets take for example an expansion valve from an AC, does the fluid do work when passing through the valve or does it not even need to do work in order to cool down. What is the lowest temperature that the fluid can...
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