Fluid Definition and 1000 Threads

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. 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)...
  2. 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...
  3. 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? ...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. P

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

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  9. adoion

    Question about fluid expansion

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  10. 2

    Hydrostatics: What remains the same in a fluid?

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  11. C

    How to Determine Pi Groups for Fluid Flow Through an Orifice

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  12. 462chevelle

    Can Taking Fluid Mechanics Without Completing All Prerequisites Work?

    I was wondering if I could get you guys advice on something. My school only offers fluid mechanics every other Fall. This spring I'm taking physics 1, calc 2, and chem 2. In the fall I'll for sure be taking physics 2, and calc 3, I could take rigid body mechanics and experimental techniques, but...
  13. Y

    Fluid mechanics question--slip boundary condition for gas?

    In solving the Navier Stokes equation, the typical boundary condition imposed on the tangential velocity at a solid surface is that of no-slip. However, it is known that for gaseous flow there always exists a non-zero velocity near the wall, especially at relatively big Knudsen number. Is there...
  14. J

    Help with entrance effects for fluid please

    Can anyone tell me how significant are entrance effects for a fluid entering a circular pipe? Like the fully developed region, laminar region etc. comparison between these regions...
  15. A

    Fluid dynamics: Reynolds Number, Drag Constant

    I completed 4a successfully, and with 4b, i have 2 queries: a)why can't I let Reynolds # equal to 2.19 x 10^5 (from part a) then simply sub v=4 instead of 5m/s and rearrange for viscosity? I tried it this way first and got a very wrong answer. Why do we, essentially, need to work backwards to...
  16. A

    Fluid dynamics: head losses and pressure

    see I worked through 3a) and I was comparing answers, I saw that they omitted v2 (5m/s) their explanation was because it was "defined in the question" I'm not sure what that means 3)b I tried understanding what's going on but I am clueless unfortunately, how exactly did they get 12.1m ? Where is...
  17. E

    Water Flow in Pipe: Velocity & Height Calculation

    1. Water is flowing in a pipe at 5ms-1, the end of the pipe is held vertically and discharges into the atmosphere, the velocity of water discharging from the pipe is: a=0.25 b=1.3 c=5 d=25 2. The water in the question above will rise to a height in metres of: a=1.3 b=0.25 c=25 d=13 I will be...
  18. C

    The weight with a fluid: center of mass or force at bottom?

    Homework Statement It is a question I asked to myself because I need to reply to another one. I imagined this case: http://imageshack.com/a/img912/7730/R964Vq.png The step2 needs the energy E1, the step3 needs nothing because the gravity is 0 (I imagine the device between the Earth and the...
  19. A

    Fluid mechanics and pipe flow questions

    < Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown > Pics are attached, my concerns are with question 4 and 5. For q4 -which way is flow? How do we know? -the working then goes on to say that energy loss is compensated by increasing in...
  20. C

    What force makes fluid flow faster in a smaller pipe?

    Thinking of individual fluid particles, my guess is that the "force" is simply particles backing up somewhat at the constriction point and contributing a higher proportion of collisions on particles ahead of them in a direction down the pipe. As the average movement of the particles is directed...
  21. M

    Fluid Dynamics - Momentum Equation for Area Change

    Hello :) My question concerns a control volume with a changing area. The momentum equation: p1A1-p2A2 = ṁ(V2-V1) is applied to the control volume. The image shows the equation found when applying the above momentum equation to the control volume: The bit I'm having difficulty with is the part...
  22. A

    Calculation of fluid pressure through water flowing pipe?

    HI. I'm confused in how to find pressure in horizontal Pipe theoretical. Pipe having 90mm dia and water flowing through 3m/s. If I'm insert one plate in pipe having surface area 'x', then how much pressure acting on the surface of plate by water? please explain me.
  23. STEMucator

    Calculating Volume of Fluid Flowing in Pipe

    Homework Statement A fluid flows through a pipe. The flow varies with time. We want to estimate the volume of fluid (##V##, in ##L##) that passes through the pipe between time ##t = 10 s## and ##t = 14 s## (i.e. we want to integrate the flow between these times). The available instrumentation...
  24. W

    Solving the Fluids Straw Problem: Compute Water Fraction in Ideal Gas Model

    Homework Statement This problem pertains to the drinking straw trick. You decide to place your finger over a 20.0cm straw. 95.0% of the straw is filled with water, while the top is full of air. Treating the straw as an ideal gas, compute fraction of the straw that is filled with water when the...
  25. R

    Power required to move a glass bead in a viscous fluid

    Homework Statement A bead of radius R(=5 μm) is trapped by an optical beam and moved through a viscous fluid at a speed vd of 20 μms-1. If the viscous drag is given by Stokes law: F_{d}=6\pi \eta Rv_{d} obtain an expression for the laser power (intensity). If the process only has an...
  26. B

    What is the kinetic energy of a block as water pours out of a container?

    Homework Statement A block of mass m is connected to a massless rod and plunger of area A1 on a cylindric container of water. At the bottom of the container there is a pipe that leads to an opening of area A2 where the water pours out at a velocity v. The block starts at rest with the...
  27. T

    Drag force on a sphere moving through a fluid

    A body moves through a fluid, a retarding force due to turbulence may be experienced. In case of a sphere of radius R moving with speed v through a stationary fluid of density p which it at rest, this force is given by F = kp (R^2) (v^2) k is a constant. Why F is proportional to kp (R^2) (v^2) ?
  28. Z

    Fluid Statics: Find vertical and horizontal forces in tank

    Homework Statement The tank shown in the figure is filled with water and fastened to the ground. There is a small opening on top of the semi-spherical part of the tank. a) What is the magnitude of the horizontal force on the screws? Explain using a free body diagram. b) Consider the proper...
  29. K

    A basic fluid mechanics concept that's puzzled me for years

    And it seems like it's so straightforward for everyone else, which is incredibly frustrating. It's about the relationship between pressure and flow rate of a fluid moving in a pipe or closed system. Often what I've heard is, they have an inverse relationship...but then there are cases where...
  30. M

    Probe/anemometer for measuring flow speed and direction?

    Hi, I'm trying to measure the steady state velocity field behind the wake of a bluff body in the wind tunnel. My uni is equipped with 4-hole cobra probes which is capable of receiving flow within a 45 degree cone of acceptance. As the base of a bluff body dominated with re-circulating flow...
  31. R

    Air Jet Fluid Mechanics Experiment

    Hi all, Recently did a lab experiment where we had a nozzle pointing vertically upwards at a flat plate normal to the direction of the flow of air. The plate had a spring gauge on it so that the force of the air on the plate could be measured. The plate was moved to various distances above the...
  32. Roodles01

    Fluid Statics - net upward force

    Homework Statement Find magnitude of net upward force on a cube in terms of l, ρ (rho), g and h. then show that h = m/ρl2 A solid cube, mass m, side length l, is placed in a liquid of uniform density, ρ(rho), at a depth h0 below the surface of the liquid, which is open to the air. The upper...
  33. Roodles01

    Fluid Force on a Cube at Depth h0: Calculating Pressure and Magnitude of Force

    Homework Statement A solid cube, mass m, side length l, is placed in a liquid of uniform density, ρ(rho), at a depth h0 below the surface of the liquid, which is open to the air. The upper and lower faces of the cube are horizontal. Find the magnitude of force, Fs, exerted on each vertical...
  34. S

    Fluid mechanics- High Reynolds number flows over bodies

    A 40 km/hr wind is blowing parallel to a storage facility , as shown in the figure. estimate the normal force on a 0.5-m high, 1-m long window if the front door is left open. assume the windspeed along the outside of thewindow is 1.2 U. Air density is 1.22 kg/m^3. There's a picture that...
  35. J

    Fluid Mechanics Viscous Dissipation

    I am trying to find an expression for viscous dissipation for burger's vortex Velocity field which only has velocity component in the V theta direction. I'm confused as to which equation for viscosity dissipation is correct. I am seeing a lot of different things tau:S, tau:delV..which one is...
  36. A

    [Conceptual Question] Fluid Mechanics Analysis of Pipe Flow

    Homework Statement As shown in the figure, if the pipe net work is shifted bodily by 10m vertically up the tank, and all the other conditions remain the same as the previous figure. Will the volume flow rate change? Or I rephrase it as, in the calculation of elevation head of pipe flow, is the...
  37. P

    How strong are fluid experiments in restoring determinism?

    I am referring to this article:http://www.quantamagazine.org/20140624-fluid-tests-hint-at-concrete-quantum-reality/ Only a handful of phycisists (John Bell being one of them) took the Bohm-interpretation of QM seriously, given it had no scientific falsification, Are those views likely to change...
  38. T

    Fluid Dynamics - Rate of Change of Momentum question

    Homework Statement A vertical jet of water of 3cm in diameter impinges upon a horizontal flat plate with a velocity of 4m/s, and all of the water spreads out horizontally. Find the force exerted on the plate. Homework EquationsThe Attempt at a Solution I am not 100% sure how to tackle this...
  39. A

    MATLAB MATLAB code for Computational Fluid Mechanics

    Hello guys, I'm writing to get some help on an exercise I've been thinking but I can't get to solve. I have to write the code for the Example 8.5 of the book White, Fluid Mechanics. Here is the problem and the solution I have to obtain. It is about one duct that has three sections in which I...
  40. O

    Why does the pressure of a fluid in motion change?

    Hi everyone, I'm new here and I have a question to all the physicists out here in the forum. I'm an aerospace engineering student and there is something that has been bothering me for quite a while. That is: Why does the static pressure of a fluid in motion change? Don't get me wrong, I'm...
  41. G

    Bernoulli Principle and fluid velocity

    I have been trying to fully understand this concept of Bernoulli's Principle , the Venturi effect and fluid velocity and energy. I need to grasp this to develop an idea that I have been working on. 1. As water is forced down a narrowing pipe, as the pipe gets more narrow, it means it losses...
  42. P

    Schools Computational Fluid Dynamics in Physics Graduate School

    I want to go to physics grad school, but I also want to be ready to go to into CFD for industry if academia doesn't pan out - what area of physics would prepare me best for that?
  43. H

    Why is Resistance in Fluid Flow inversely related to r^4 rather than just r^2?

    So Volume Flow Rate (Q) = (P2-P1)/R where R is the total resistance of the system. R is directly proportional to Length and inversely proportional to surface area, and the inherent resistance (viscosity) of the fluid. But R =nL/r^4. r^4 rather than r^2. So there has to be another factor...
  44. G

    Torque due to static fluid- Transport Phenomena

    1. Homework Statement Calculate the torque on the dam about the origin (Picture attached) due to the pressure force of the fluid. Homework Equations Pressure force is correct (dF) The Attempt at a Solution [/B] I have solve it; however, I am not sure if I calculated over the origin asked...
  45. E

    Lubrication Theory: Fluid Flow and Integration

    Basically, I'm modelling the flow of a "coating" process -- a fluid flow between a flat moving plane and a stationary cylinder, 2D, cartesian coordinates. Subscript 0 is the at the minimum height b/w the plane and the cylinder, and subscript c is at the point at which the flow leaves the moving...
  46. Kushwoho44

    Fluid Mechanics: Dimensionless Groups Question, explain an outlier

    Homework Statement Hi guys, I need to explain the outlier point here, which has been shaded in the excel spread sheet when comparing the two dimensionless groups, The dimenionsless group, drag-coefficient is given by Drag/(density*V^2*D^2) and dimensionelss group, spin parameter, is given by...
  47. M

    Science-Based Fluid Mechanics Recomendation

    Lately I have found an interest in fluid mechanics and found Landau's Fluid Mechanics text. Despite know it wasn't introductory, I decided to give it a try before deciding I need something before it. Is there a science-like (as in not engineering) fluid mechanics textbooks that would help...
  48. N

    Calculate the difference in height of the fluid levels

    Homework Statement The figure shows a schematic drawing of an open ended well-type manometer. Attached to one end of the manometer tube is a well (a reservoir with a higher crossectional area compared to that of the tube). The manometer is filled with a fluid with an SG = 2.95. The manometer...
  49. S

    Mechanical engineering and fluid mechanics, thermodynamics

    I'm curious as to roughly how many mechanical engineering graduates have found jobs where they utilise the knowledge they gained in fluid mechanics, thermodynamics and heat transfer as part of their university degrees. Reason I'm curious is because, from my class, I'm not actively aware of...
  50. T

    Fluid pressure on an object in open system

    Hello everyone, I have a physics question on pressure exerted by a fluid onto an object (see attachment). I would like to know how I can calculate the total pressure exerted on an object in a vessel by flowing fluid (water) with an open outflow. It has been too long since I took college...
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