Explore BrainMass

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.

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.

Calculating Stream Flow in a Watershed

Following the stream cross section (ft2) and the stream velocity (ft/sec) allows us to calculate the stream flow (ft3/sec). The watershed runoff during a storm is 3.5 ft. high and flows in 18 ft. wide channel. The velocity is measured at 1.2 feet per second (fps). What is the flow rate of the water in cubic feet per second?

volumetric flowrate

A 7cm pipe gradually narrows to 3cm. When freshwater density 1000kg/m3 flows through the pipe constriction the pressure drops from 32kN/m2 to 20 kN/m2. What is the volumetric flowrate in m3/s?

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

Simple Fluid Mechanics

You have a liquid sitting between 2 plates. A shear stress is applied to the top plate causing it to move. (the bottom plate is rigid) This fluid has a yield stress (ty) bellow which it will not move. Assume that the liquid, where in contact with the plate, moves at the same velocity as the plate. Also assume that the fluid h

Pressure at a point in a horizontal tube

Water is flowing in a horizontal tube. The pressure at a point is 0.01 m of Hg at which the velocity is 0.6 m/s. What is the pressure at a point where the velocity is 0.8 m/s ?

Physics Fluid Dynamics

A small plane, having a mass of 3000 kg, is flying in air of density 1.0 kg/m^3. Air moves over the top and bottom surfaces of the wings at 160 m/s and 130 m/s, respectively. What is the net minimum wing area needed?

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


A diver is 10m down in the ocean and the pressure gauge on an air tank reads 75kPa. At what depth will the gauge pressure read zero? What does this mean?

Fluid Mechanics

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

Difference in pressure on the bottom of a swimming pool at opposite ends.

A swimming pool is 50 meters long by 23 meters wide and is lees deep at one end than at the other. The depth at the shallow end is 1.22 meters, and the depth at the deep end is 4.35 meters. The slope is continuous (smooth) from one end to the other. What is the difference in pressure on the bottom at opposite ends of the pool?

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.