0
Fluid Dynamics
The study of the motion of fluids (liquids and gases) and the forces causing this motion, Fluid Dynamics has several subdisciplines, including hydrodynamics and aerodynamics. To ask and answer questions about Fluid dynamics and its subdisciplines, come on in to the Fluid Dynamics category.
621 Questions
What is the definition of velocity gradient?
With respect to material being sheared, velocity gradient is the change dv in relative velocity v between parallel planes with respect to the change dr in perpendicular distance r throughout the depth of the material. Velocity gradient has the same dimensions as rate of shear, which is reciprocal seconds.
Explain why objects moving in fluids must have special shapes?
When objects move through fluids, they have to overcome friction acting on them. In this process they lose energy. Efforts are, therefore, made to minimise friction. So , objects are given special shapes.
Why does water pressure increase with surface area and fluid density?
Water pressure increases with surface area because a larger surface area means the force is distributed over a greater area, resulting in higher pressure. Fluid density also affects water pressure because denser fluids have more mass per unit volume, increasing the pressure at a given depth due to the weight of the fluid above.
Which one will determine how much water will be displaced - mass or volume?
Volume will determine how much water will be displaced. The volume of an object dictates how much space it occupies, which in turn determines the amount of water it displaces when submerged. Mass alone does not directly affect water displacement.
The term high pressure is extremely vague - as is low pressure. The answer to the question of pressure classification is based on what fluid and the type of handling equipment. Commericial and industrial hydraulics traditionally recognize pressures of 3,000 PSI and under. So when discussing hydraulic oil systems high pressure is anything above 3,000 PSI. In consumer pressure washers anything above 2,000 PSI would be considered high pressure. In industrial triplex pump applications, 2000 PSI would be considered very low pressure. Gases are also considered fluids, and gases have completely differrent pressure classifications. In summary, when asking about a pressure classification one must include the additional information - namely the fluid and the application.
Will a sub kiloton Atomic Bomb make a mushroom cloud?
Yes. In fact, any large explosion(atomic or otherwise)which occurs on or near the ground will cause a mushroom cloud. This is because the explosion creates a mass of superheated air and debris, which will expand and rise upwards because its density is less, and its temperature higher, than the surrounding air; basically the same principle that causes hot-air balloons to rise. This is what gives you the iconic "mushroom" cloud. About the only time you wouldn't expect to see such a cloud is if the detonation occurs deep under ground or water, or at extremely high altitudes.
Importance of graphical methods for analysing an experiment?
The answer is obvious, a picture is worth a thousand words. Being able to lay out in pictora or graphical form the meaning and results of the data make it clear often to laymen. It is also a check on the work in mathematically analysing methods and results.
Why is there sound when wind blows past a telephone wire?
The wind pushing past the wire creates a low pressure zone on the downwind side of the wire.
As air rushes into this low pressure zone, collisions between pressure fronts creates vibrations in the air, perceived as sound.
What is the distance a piston travels called?
The distance a piston travels within the cylinder is called the stroke. It is the distance between the top dead center (TDC) and the bottom dead center (BDC) positions of the piston.
What is the study of how fluids move?
The study of how fluids move is known as fluid dynamics. It involves investigating the behavior of liquids and gases in motion, as well as the forces and interactions that cause this movement. Fluid dynamics is essential in various fields such as engineering, meteorology, and oceanography.
Assuming that you and the anchor are both in the boat and floating on the sea, the level of water would go down once you throw the anchor into the water.
The logic behind this follows from two facts which, if not known, would make it almost impossible to answer this question.
When an object floats on a liquid (let's say water), it displaces water equal to its own weight. Also if an object is submerged in water, it displaces water equal to its own volume.
Therefore, as the anchor is extremely heavy, it displaces a great deal of water when it is floating on the boat, but when you drop it into the water (because its volume is quite small), it displaces less water (or fluid) and so the level of water would rise a lot less compared to its fall, which would be greater.
Now you may be wondering how I can make the assumption that the volume is small. Well, you have to assess the density of the substance. Density = mass/volume; the anchor has a high density, and water has a lower density.
Lets assume, for all intents and purposes, that the density of water is 1 and that of the anchor is 2.
So the anchor has a greater mass than the water per unit of volume:
1=y/x
2=2y/x
It also has a smaller volume per unit of mass relative to water, of course.
1=y/x
2=y/0.5x
(y=x=1)
So relative to the water, you can say that the anchor has a greater mass than it does volume, and so it displaces more water in the boat than in the water.
What factors determine the maximum altitude of an airplane?
Short Answer:
An airplane maintains altitude by producing enough lift to counteract its own weight. So the amount of lift an airplane produces determines how high it can climb. Lift is produced by accelerating air in a downward direction. At higher altitudes the air is less dense so a larger volume must be accelerated downward to produce enough lift to keep flying. This can be done in two main ways; flying faster or having longer wings. The faster you fly the more air you pass through so the more you can accelerate downward which generates more lift. The longer your wings are the more surface area you have to generate lift so you can maintain altitude. You can also make your plane lighter while maintaining its top speed and wing length by carrying less fuel and cargo or using smaller pilots. Given the same speed and wing length a lighter plane can maintain altitude in less dense air so it can climb higher than a heavier plane that is traveling the same speed.
Longer Answer:
Lift can also be generated by an airplanes engine if that engine is pointed towards the ground. In fact some airplanes can fly straight up by generating all their lift with their engine and none with their wings. So with a powerful enough engine there is not limit to how high an airplane can fly. However most airplanes use "air breathing" engines that burn fuel with oxygen supplied by the atmosphere. The higher you go the less air there is in a given volume of sky so the less oxygen is gets sucked into the engine to burn fuel. Pilots have reduce the fuel flow to their engines as they go higher since the extra fuel would be wasted with no oxygen to burn it and it would tend foul the engine with partially burned residue making it run less efficiently or stalling it out completely. With less fuel to the engines the airplane slows down until it produces exactly enough lift to maintain its altitude. It's possible to get a little higher by diving and speeding up then pulling up hard and letting the airplanes momentum carry it to a higher altitude temporarily but when it slows down it will drop back to an altitude where lift equals the planes weight at the highest speed possible given the amount of oxygen in the air at that altitude. If a plane could get going over 25,000 mph (33 times the speed of sound) and and coast out of the atmosphere before it slowed down much below that speed it would keep going since it would be above escape velocity needed to get out of the earth's gravitational field. If it were pointed in the right direction and kept going faster than about 17,000 mph it could go into orbit in space.
Rocket engines carry their own oxidizer which contains the oxygen to burn the fuel so they can run even in the vacuum of space above around 100 km (330,000 feet). The only limitation on altitude for them is how much fuel they can carry before they are too heavy to lift themselves.
So the real answer to the question is that the main factor determining maximum altitude for an airplane is how high the engine can go before the air gets too thin to maintain enough velocity to balance the plane's weight against lift. Longer wings and less drag (a more aerodynamic shape) will help the same engine fly higher as will a lighter plane.
An airplane with a rocket engine that does not breath air is limited by how much fuel it can lift when starting off. Too much fuel weight and the plane won't take off until the excess weight of fuel has been burned. Once the rocket plane lifts off the altitude limit is determined by how fast the plane can get going before running out of fuel. If it can accelerate to 25,000 mph or faster it can go forever. If it can go at least 17,000 mph it can go into orbit in space more than 330,000 feet up (62 miles). Otherwise you can use rocket science equations to figure out how high it can get before it starts falling using the vehicle mass, rocket engine thrust, fuel burn rate and atmospheric drag. This is a complex calculation because the mass, and atmospheric drag change as a function of altitude and the fuel burn rate and engine thrust usually don't stay the same throughout the flight.
A hydraulic press is a machine that uses fluid pressure to generate force and apply it to compress materials. It consists of a chamber with hydraulic fluid that works to amplify force through a piston. Hydraulic presses are commonly used in industrial processes such as forming, molding, and punching.
Why doesn't body density change when submerged in water?
The body's overall density remains the same in water because the mass of the body and the volume of water it displaces are equal, following Archimedes' principle. When submerged, the body displaces an amount of water equal to its own weight, which keeps the body's density constant.
Sound waves from a radio generally travel in what medium?
Sound waves from a radio typically travel through the air as it is a medium that allows for the propagation of sound waves. Sound waves are generated by the radio transmitter and then travel through the air as vibrations in the form of pressure waves to reach the receiver.
The work done on the gas during compression is given by the formula W = PΔV, where P is the average pressure and ΔV is the change in volume. So, the work done on the gas during compression is (1123000 + 2445000)/2 * (20.81 - 11.25) = 10600475 J. Since no heat is transferred to the environment and the process is adiabatic, the change in internal energy of the gas is equal to the work done on the gas, so ΔU = 10600475 J.
What forces act upon swimmers?
Swimmers experience forces such as drag, buoyancy, and propulsion. Drag is the resistance of water against the swimmer's movement, while buoyancy helps to keep the swimmer afloat. Propulsion is the force generated by the swimmer's movements to propel themselves through the water.
What is the relation between alternate depths in rectangular open channels?
In rectangular open channels, alternate depths refer to two different water depths that the flow can take within the channel. These depths are symmetrically positioned about the channel bottom and are a result of the conservation of energy in the flow. The alternate depths occur when the flow transitions between supercritical and subcritical flow conditions within the channel.
How do you go about calculating buoyant force?
This is fairly simple. First calculate the amount of fluid displacement of the object, i.e. it would displace 10 cubic feet of fluid if completely submerged. Next, determine the weight of the fluid, i.e. salt water weighs 64 pounds per cubic foot. This can be used to determine the upward or buoyant force exerted on the object by multiplying the displacement by the weight of the fluid. In this example, it is 640 pounds. To determine whether an object will float or sink, simply subtract the weight of the object from the buoyant force. In this example, if the object weighs 200 pounds then the object will float since the 200 pounds of the object is met with 640 pounds of upward water force, so the object weighs 440 pounds in the water (640 - 200 = 440). If the object weighed 640 pounds, then it would be neutrally buoyant in the water and would neither sink nor float and would stay where placed (assuming no water movement, etc.) ... and if it weighed more than 640 pounds, then the object would naturally sink since it weighs more than the force of the water pushing against it.
In what matter phase are the molecules far apart and move quickly?
In a gas, molecules are relatively far apart and have the energy to move quickly.
Give the physical interpretation of the substantial derivative?
The first ∂/∂t term is called V the local derivative. The second ~· ∇ term is called the convective derivative. In steady flows, ∂/∂t =0, and only the convective derivative
The substantial derivative has a physical meaning: the rate of change of a quantity (mass,
energy, momentum) as experienced by an observer that is moving along with the flow. The
observations made by a moving observer are affected by the stationary time-rate-of-change
of the property (∂f/∂t), but what is observed also depends on where the observer goes as
it floats along with the flow (v · ∇f). If the flow takes the observer into a region where, for
example, the local energy is higher, then the observed amount of energy will be higher due
to this change in location. The rate of change from the point of view of an observer floating
along with a flow appears naturally in the equations of change.
Why two streamlines can not intersect with each other?
The direction of the velocity of a fluid at any point is taken to be tangential to its streamline at that point. When two streamlines intersect two tangents can be drawn at the point of intersection. It inturn means that the fluid has velocity in two different directions which is not possible. Therefore 2 streamlines cannot intersect.
Is zero-shear viscosity the same as maximum viscosity?
To answer my own question :), if I interpret the differentials correctly, viscosity does have its maximum when there are no shearing forces, regardless of whether the fluid is newtonian or not. So, in short, yes.
Types of motion include linear motion (movement in a straight line), circular motion (movement in a circular path), rotational motion (spinning or rotating around a central point), and oscillatory motion (repetitive back-and-forth motion).
