Term
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Definition
| flows that are completely bounded by solid surfaces. i.e. in pipes or ducts |
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Term
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Definition
| flow of unbounded fluid over a surface. such as flow over a plate |
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Definition
| flow of liquids with a free surface above. i.e. flow in a river or ditch |
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Term
| what causes no-slip condition? |
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Definition
| the viscosity of the fluid |
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Term
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Definition
| flow process in which there is no change with time inside the system or at the system boundaries |
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Term
| normal stress within a fluid |
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Definition
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Term
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Definition
| distinction between a solid and a fluid is made on the basis of the substance's ability to resist an applied shear stress that tends to change its shape. A fluid deforms continuously under a shear stress, no matter how small |
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Term
| what different forms of energy constitute total energy? |
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Definition
| kenetic, potential, and internal |
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Term
What is viscosity?
What causes viscosity in liquids and in gases? |
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Definition
| Viscosity is a measure of a fluid's resistance to deformation. Viscosity in fluids is caused by cohesive forces between molecules. In gases, it's caused by the collision of molecules. |
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Term
How does the dynamic viscosity of fluids vary with Temp?
Of gases? |
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Definition
| in liquids it decreases with temperature. in gases it increases with temp |
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Term
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Definition
| the magnitude of the pulling force at the surface of a liquid per unit length |
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Term
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Definition
| a fluid flow during which the density of the fluid remains nearly constant |
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Term
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Definition
| a fluid whose density is practically independent of pressure (such as a liquid). |
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Term
| must the flow of a compressible fluid be treated as compressible? |
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Definition
| no, the flow of a compressible fluid (such as air) is not necessarily compressible since the density of a compressible fluid may still remain constant during flow |
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Term
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Definition
| the pressure applied to a confined fluid increases the pressure throughout by that same amount |
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Term
| what is a boundary layer? |
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Definition
| when a fluid stream encounters a solid surface, the fluid velocity assumes a value of zero at the surface. The velocity then varies from zero at the surface to the free-stream value at a sufficient distance from the surface. The boundary layer is the region of flow in which the velocity gradients are significant |
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Term
| what causes a boundary layer to develop? |
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Definition
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Term
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Definition
| a continuous, homogeneous, matter with no holes. the continuum idealization allows us to treat properties as point functions and to assume that the properties vary continually in space with no jump discontinuities. |
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Term
| When can a real gas be treated as ideal? |
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Definition
| At a high temperature or low pressure relative to its critical temperature and pressure |
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Term
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Definition
| the forms of energy related to the molecular structure of a system and the degree of their molecular activity. |
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Term
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Definition
| the sum of all microscopic forms of energy. Denoted by U or u |
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Term
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Definition
| related to motion and the influence of some external effects such as gravity, magnetism, electricity, and surface tension |
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Term
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Definition
| a measure of the "resistance to deformation of a fluid due to the internal frictional force that develops between different layers of fluids as they are forced to move relative to each other |
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Term
| What is the cause of Viscosity? |
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Definition
| Viscosity is caused by the cohesive forces between the molecules in liquids, and by the molecular collisions in gases. Liquids have higher dynamic viscosities than gases. |
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Term
| What are Newtonian fluids? |
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Definition
| The fluids whose shear stress is proportional to the velocity gradient are called Newtonian fluids. (most common fluids such as water, air, gasoline, and oil are Newtonian fluids) |
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Term
| Dynamic Viscosity of Liquids |
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Definition
| decreases with temperature |
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Term
| Dynamic viscosity of gases |
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Definition
| increases with temperature |
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Term
| kinematic viscosity of liquids |
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Definition
| is practically independent of pressure |
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Term
| kinematic viscosity of gases |
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Definition
| is inversely proportional to density and thus pressure (because the density of a gas is proportional to its pressure) |
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Term
| what causes surface tension? |
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Definition
| the attractive forces between the molecules. (the surface tension is also surface energy since it represents the stretching work that needs to be done to increase the surface area of the liquid by a unit amount) |
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Term
| What is the capillary effect? |
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Definition
| the rise or fall of a liquid in a small-diameter tube inserted into the liquid. The capillary effect is proportional to the cosine of the contact angle, which is the angle that the tangent to the liquid surface makes with the solid surface at the point of contact. |
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Term
| What causes the capillary effect |
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Definition
| the net effect of the cohesive forces (the forces between like molecules) and adhesive forces (the forces between dislike molecules) |
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Term
| Is the Capillary Rise greater in small- or large- diameter tubes? |
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Definition
| Capillary Rise is greater in small-diameter tubes because they are inversely proportional to the diameter of the tube |
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Term
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Definition
| the pressure applied to a confined fluid increases the pressure throughout by the same amount |
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Term
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Definition
| Center of gravity, G, is directly below center of buoyancy B |
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Term
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Definition
| G (center of gravity) and B (center of buoyancy) are coincident |
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Term
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Definition
| G (Center of Gravity) is directly above B (Center of buoyancy) |
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Term
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Definition
| device used to measure atmospheric pressure (aka barometric pressure) |
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Term
| Does the length or cross-sectional area of the tube have an effect on the height of the fluid column of a barometer? |
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Definition
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Term
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Definition
| nonzero only for unsteady flows |
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Term
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Definition
| nonzero only for unsteady flows |
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Term
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Definition
| (v dot grad)v. can be nonzero even for steady flows. accounts for a fluid particle moving to a new location in the flow where the velocity field is different |
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Term
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Definition
| a curve that is everywhere tangent to the instantaneous local velocity vector. can be derived mathematically |
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Term
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Definition
| an actual path traveled by an individual fluid particle over some time period |
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Term
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Definition
| the locus of fluid particles passed sequentially through a prescribed point in the flow |
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Term
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Definition
| a set of adjacent fluid particles that were marked at the same instant in time |
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Term
| What is the Lagrangian description of fluid motion? |
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Definition
| In the Lagrangian description of fluid motion, individual fluid particles (fluid elements composed of a fixed, identifiable mass of fluid) are followed. Similar to that of studying billiard balls and other solid objects in physics. |
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Term
| Is the Lagrangian method of fluid flow analysis more similar to a study of a system or a control volume? |
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Definition
| Lagrangian method is more similar to system analysis. We follow a particular chunk of fluid as it moves in a flow |
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Term
| Define the Eulerian description of fluid motion |
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Definition
| In the Eulerian description, we are concerned with field variables such as velocity, pressure, temperature, etc., as functions of space and time within a control volume. |
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Term
| How is the Eulerian description different from the Lagrangian? |
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Definition
| In contrast to the Lagrangian method, fluid flows into and out of the Eulerian control volume, and we do not keep track of the motion of particular identifiable fluid particles. (This method is not as natural as the Lagrangian because the fundamental conservation laws apply to moving particles not fields) |
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Term
| What is the static pressure, P? |
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Definition
| the actual pressure of the fluid |
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Term
| What is the dynamic pressure, rhoV^2/2 |
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Definition
| The pressure rise when the fluid in motion is brought to a stop |
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Term
| What is the hydrostatic pressure rho*g*z |
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Definition
| not pressure in a real sense since its value depends on the reference level selected, and it accounts for the effects of fluid weight on pressure |
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Term
| What is the stagnation pressure? What kind of device measures it? |
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Definition
| The stagnation pressure is the sum of the static and dynamics pressures and can be measured by a pitot tube whose inlet is normal to flow. |
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Term
| What is the pressure head P/rho*g? |
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Definition
| the height of a fluid column that produces the static pressure P |
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Term
| What is the velocity head, V^2/2g? |
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Definition
| The elevation needed for a fluid to reach the velocity V during frictionless free fall. |
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Term
| What is the elevation head z? |
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Definition
| The height of a fluid relative to a reference level. |
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Term
| What is the hydraulic grade line (HGL)? |
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Definition
| The sum of the static pressure and elevation heads. P/rho*g +z |
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Term
| What is the energy grade line (EGL)? |
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Definition
| the line that represents the total head of the fluid, P/rho*g + V^2/2*g + z |
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Term
| How is the location of the HGL determined for open-channel flow? |
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Definition
| For open-channel flow, the hydraulic grade line coincides with the free surface of the liquid. |
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