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Fluid Mechanics

Fluid dynamics is the study of fluid flow. It has two subdisiciplines, aerodynamics and hydrodynamics. Fluid dynamics is used in a wide range of applications. One can calculate the forces on aircrafts, determine flow through pipes or predict weather patterns by using fluid dynamics. Some principles from fluid dynamics are even used in traffic engineering. Fluid dynamics is cross disciplinary and studied in a wide variety of ways.
The foundation of fluid dynamics is the conservation laws. These laws are based off classical mechanics but modified in quantum mechanics and general relativity. From these principles the Reynolds Transport Theorem was created. To model more complex equations of Newtonian fluids, physicists use the Navier-Stokes equations which model the behavior of fluids in a series of differential equations. Computational physics is often used in order to solve these complex problems in which stress and velocity are dependent on linearity.

Compressible Fluid – The density changes with a change in pressure or temperature.
Incompressible Fluid – The density change is negligible with a change in pressure or temperature.
Viscous Flow – The fluid friction does not have significant effects on the fluid motion. Viscous flow indicated the Reynolds number is low.
Inviscid Flow – The fluid Friction has significant effects on fluid motion. The Reynolds number is high.
Steady Flow – The fluid properties throughout the system do not change.
Unsteady Flow – The fluid properties change through the system.
Laminar Flow – The fluid flow is in parallel layers with no disruptions. The Reynolds number is less than one.
Turbulent Flow – There is recirculation and apparent randomness of flow. The Reynolds number is greater than one.
Newtonian Fluid – The viscous stresses arise from the flow at every point. These stresses are proportional to the local strain rate over time.
Non-Newtonian Fluid – The viscosity of the fluid is dependent on shear rate.

Categories within Fluid Mechanics


Postings: 14

The study of air and other gases in motion.

The Physics of Pressure Washers

A popular brand of pressure washer claims to deliver 330 litres per hour of water at a pressure of 80 bar, drawing 1,400 W of electrical power in the process. Pressure washers of this type are made up of an electric motor that drives a small compressor to pressurize water fed into it through a garden hose. a.Show that the amoun

Fluid Mechanics: Airplane Wing Design

One of the most important applications of fluid dynamics is in the design of airplane wings. In this SLP, we'll introduce some basic terminology and take a quick look at the relationship between angle of attack, airspeed, and lift. Go to the NASA GRC (2010) link on the Background page, which is a simulation called FoilSimII

Fluid Mechanics: Static and Dynamic Pressures

1. A laboratory receives a sample of a metallic alloy composed of aluminum and magnesium. The sample is a solid cylinder with a diameter of 2 cm and a length of 5 cm. Its mass is 15.70 g. What is its density? What is its specific gravity? 2. A boat has a dry weight of 3500 lbs. How many liters of water does it displace?

Condition for Irrotationality of a 2-d Ideal Fluid Flow

See the attached file. Working from first principles show that the condition for irrotationality of a two-dimensional ideal fluid flow is given by: delta(u)/delta(y) = delta(v)/delta(x) Hence, define in mathematical terms the velocity potential psi, and show that potential lines of constant psi are perpendicular to st

Apparent Weight and Actual Weight

Please help with the given problem: ** Please see the attached file for the figure depicting the described problem ** You must compute the ratio of the actual weight of the crown (W_actual) and the apparent weight of the crown when it is submerged in water (W_apparent). See whether you can follow in Archimedes' footsteps. Th

Mechanical Engineering Design

1 The carbon dioxide in a nuclear reactor is maintained at 40 bar (gauge) and 70 deg C. Estimate its density, specific weight and relative density. 2 A water-filled manometer indicates a pressure differential of 2100 N/m2. What is the difference in elevation of the vertical limbs?

Problems on Fluid Dynamics

Two problems on fluid dynamics: Problem 1: Water flowing in a pipe with two sections with different cross section areas. To determine pressure, velocity and flow rates in the two sections. Problem 2: Water in a tank being siphoned off. To determine velocity, pressure, flow rate etc.. See the attached file.

Four problems on mechanics.

Please see attached file for full problem description. #16 A 58-kg skier is going down a slope oriented 35° above the horizontal. The area of each ski in contact with the snow is 0.13 m2? Determine the pressure that each ski exerts on the snow. #22 Measured along the surface of the water, a rectangular swimming pool has

Head-box issues in Pulp Mill : Theoretical Modelling Question

The process in question uses a centrifugal fan pump to convey a 1000 gallon per minute flow containing 2% finely ground wood pulp to a head box...which in turn is supposed to ocnvert turbulent flow to laminar flow and then deposit the water & pulp slurry on a high speed moving wire in order to form a wet fiber mat. However, t

Friction, Drag Force, and Heat Transfer

Air at 22C and at pressure of 120 kPa is flowing over a flat plate with a velocity of 4.5 m/s. If the plate is 50 cm wide and the surface in contact with the air is at 82C, calculate the following quantities at x = 42 cm: (a) the local friction coefficient; (b) the average friction coefficient; (c) the drag force; (d) the local

Fluid mechanics lab-experiment

Included are my labs sheets, data I calculated, and a poor sketch of a graph at this stage. On page 52 would someone please help me to answer all the questions and the one pertaining to my graph? See attached file for full problem description.

Elastic Moduli and Pascal's Principle and Fluid Dynamics

Question 1: A bimetallic rod is composed of brass and copper. a. If the rod is subjected to a compressive force, will the rod bend toward the brass or the copper? Why? b. Justify your answer mathematically if the compressive force is 5.00 X 104 N. Question 2: A water dispenser for pets has an inverted plastic bottle. When a

Similitude Test and Dimensional Analysis

We are designing a new type of racing boat hull. In the model tests in a towing basin we will use a model one-tenth the size of the actual boat. See attached file for full problem description.

Determining the weight of an automobile

The four tires of an automobile are inflated to a gauge pressure of 2.17e+5 Pa. Each tire has an area of 0.0271 m^2 in contact with the ground. Determine the weight of the automobile.

Fluid Dynamics and Forces

A vane on the moving cart deflects a 10 cm jet of water as shown. The initial speed of the water jet is 20 m/s and the cart moves at 3 m/s. The vane splits the jet evenly (1/2 at 45º and 1/2 at 90º) What forces are exerted on the vane by the jet? (See attached file for full problem description with diagram)

Moment of Inertia of a Sphere

A sphere consists of a solid wooden ball of uniform density 800kg/m^3 and radius 0.20 m and is covered with a thin coating of lead foil with area density 20kg/m^2 . Calculate the moment of inertia of this sphere about an axis passing through its center.

Navier-Stokes Equations

Describe the additional assumptions , conditions ,and steps required to derive the Navier-Stokes Equations from the momentum equations. Use as little mathematics as possible.

Density of Fluid

If h1 = 0.43 cm and h2 = 4.14 cm and the blue liquid in the U-tube is water (1000 kg/m3), what is the density of the green liquid?

Fluid Mechanics: Ideal and viscous flow of fluids

1/ water is flowing smoothly in a closed pipe system. At one point the speed of the water is 3.0m/s, while at another point 2m higher the speed is 5.0m/s. (a) if the pressure is 50kPa at the lower point, what is the pressure at the higher point? (b) What would the pressure at the upper point be if the water were to stop flowing

Find the volume of the paperweight.

1. A pirate in a movie is carrying a chest (0.30 m X 0.30 m X 0.20 m) that is supposed to be filled with gold. To see how ridiculous this is, determine the weight (in newtons) of the gold. To judge how large this weight is, remember that 1 N = 0.225 lb. 2. An airtight box has a removable lid of area 1.3 X 10^-2 m^2 and ne

Fluid mechanics Questions - Manning's Formula

11) The angle between the tow sloping sides of a standard triangular weir is 60 degrees. When the head of the crest of the weir is .525ft, the rate of discharge, in cubic feet per second, would be? .405 cfs, .331 cfs, .368 cfs, .294 cfs. 12) The diameter of a circular sewer is 42 in., and the rate of slope is .

Fluid Mechanics

6) A sewer 24 in. in diameter is made of concrete pipe for which the value of n may be taken as .014. The rate of slope is .0007, and the depth of the liquid is 18.0 in. what is the rate of discharge. 6.3 cfs., 5.1 cfs, 5.5 cfs, 4.2 cfs 7) The Reynolds number for liquid flowing in a pipe is 28,600. The frictio

Discussing a Bernoulli Problem

Please help understanding the effects of a stream which is flowing through a tube. I've prepared the following problem for discussion. Using Bernoulli's equation and the steady flow momentum relation to calculate the net force on a tube from a dynamic pressure drop and a water flow stream flowing through ta tube. See the a

Venturi meter - Similitude problem

A model of a venturi meter has linear dimensions one-fifth those of the prototype. The prototype operates on water at 20 degrees Celsius, and the model on water at 95 degrees Celsius. For a throat diameter of 600 mm and a velocity at the throat of 6 m/s in the prototype, what discharge is needed through the model for similitude?

Volume and Cubic Meters

A volume of 100.cm3, is how many cubic meters? a. 1.00 b. 1.00 x 10^-2 c. 1.00 x 10^-4 d. 1.00 x 10^-6 e. 1.00 x 10^-3