# Shared Flashcard Set

## Details

Fluid Mechanics
Test 1
39
Mechanical Engineering
09/29/2010

## Additional Mechanical Engineering Flashcards

Term
 When do we use the integral approach? (Not differential)
Definition
 When we only want the gross behavior of the device, not the detailed behavior of the flow
Term
 When do we use the differential form to solve a fluid mechanics problem?
Definition
 When we want to determine the detailed behavior of the flow
Term
 Density is defined as
Definition
 mass/volume kg/m^3
Term
 Explain the continuum assumption
Definition
 Fluid is approximated as a continous media (ignores molecular composition).  Fluid properties are then defined at each 'point' in time. We define the point by creating a control volume that looks like a point on a macroscopic level, yet is large compared to the molecules
Term
 Define pressure
Definition
 scalar quantity that acts normal to a surface. Force/area
Term
 Define static pressure:
Definition
 local thermodynamic pressure in a moving fluid: or the pressure at a nominated point in a fluid (wikipedia)
Term
 Define Dynamic pressure, q
Definition
 Kinetic energy per unit volume:   q = ρu²/2 (pascals)
Term
 Isentropic flow:
Definition
 constant entropy
Term
 Total Pressure, p0
Definition
 (static pressure, p + dynamic pressure, q)   -represents the total energy available in flow:   p0 = p +q
Term
 Stagnation point
Definition
 point in flow where velocity is zero
Term
 Pressure Coefficient, Cp
Definition
 Dimensionless pressure relative to reference value   Cp =(p - p∞)/[(1/2) ρ∞*u∞2 ]
Term
 Dynamic viscosity, μ
Definition
 Measures the 'stickiness' of the molecules and their resistance to motion
Term
 Kinematic viscosity
Definition
 the Dynamic viscosity, µ, over pressure, ρ   µ/ρ
Term
 No slip condition (in relation to viscosity)
Definition
 FLuid molecules in contact with a solid surface have the same mean velocity of that surface
Term
 Laminar
Definition
 Nearly parallel layers sliding over one another
Term
 Turbulent
Definition
 Complex fluid motion.  Characterized by a range of eddy like motions, bounded in size by width of flow at upper end and viscosity at lower end
Term
 Divergence
Definition
 divΦ = (Nobla). u
Term
 Curl
Definition
 curl u = (Nobla) x u
Term
 Explain Stoke's theorum
Definition
 Relates the surface integral of the curl of a vector field to the line integral of the vector field around a boundary curve.   The integral of the curl of the velocity u over a surface dA is equal to the line integral of u integrated over ds (tangent to the bounding curve)
Term
 Explain Gauss' Theorum
Definition
 also known as the divergence theorum...   The divergence of u integrated over a volume bounded by a surface A is equal to the vector u integrated over the area.
Term
 3 types of flow lines
Definition
 Pathline Streamline Streakline
Term
 Pathline
Definition
 A line traced out by a single fluid element
Term
 Streak Lines
Definition
 A line of fluid elements that all pass through a common point in space
Term
 Stream Lines
Definition
 A line drawn in flow such that the tangents to the line are parallel to the local velocity vector at that instance in time
Term
 Lagrangian Frame
Definition
 Track fluid particle as it moves trough space
Term
 Eulerian Frame
Definition
 Identify a volume in space and time (control volume) and keep track of fluid in that fixed volume
Term
 Fluid Statics
Definition
 The study of fluids at rest and in stable equilibrium   Note: A fluid cannot stay at rest under the presence of a shear force
Term
 Describe how pressure works on a fluid in static equilibrium:
Definition
 If we look at an infinitesimally small cubic fluid element, a stable equilibrium demands that the pressure on any side must be equal, since the fluid would move in the direction of the resulting force otherwise.
Term
 Pascal's Law
Definition
 Pressure exerted in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the initial pressure ratio remains the same
Term
 Explain the Hydraulic Press
Definition
 In a hydraulic press, we have a two froces and two areas.  The forces come from the force on the plunger and the weight of the ram.  The areas correspond to the ram and plunger.  Thus, the force/area ratios are equal for each element.   Fplunger/Aplunger=Wram/Aram
Term
 Hydrostatic Pressure
Definition
 Is the pressure exerted by a fluid at equilibrium due to the force of gravity   Δp = -ρgΔh   or   δp/δV=-ρg
Term
 Intuitive derivation of Hydrostatic Pressure
Definition
 The force acting on an infinitesimally small cube of fluid at equilibrium is equal to the weight of the column of fluid above it   Δp = -ρgΔh
Term
 Absolute pressure, Pabsolute=
Definition
 Pabsolute = Patm + Pgauge
Term
 Equation for streamline
Definition
 dx/ds = u  (x and u in vector form)
Term
 Streakline
Definition
 dx/dt = u(x(t),t)  , Τ ≤t
Term
 Equation for Streakline
Definition
 dx/dt = u(x(t),t)  , u is in vector form
Term
 Explain Archimedes principle
Definition
 Any object wholly or partially submerged is buoyed up by a force equivalent to the weight of the water displaced   Buoyancy = weight of water displaced   Fbuoy= ρgV
Term
 What constitutes a submerged body in stable equilibrium?
Definition
 Center of buoyancy is above center of gravity
Term
 Hydrostatic forces (on surfaces)
Definition
 The resultant force Fr of a static fluid due to the hydrostatic pressure distribution on the surface   abs(Fr) = (1/2)ρgh^2
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