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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.
1,960 Questions
How does surface tension work?
Asked by Wiki User
Surface tension is a property of the surface of a liquid. It is what causes the surface portion of liquid to be attracted to another surface, such as that of another portion of liquid (as in connecting bits of water or as in a drop of mercury that forms a cohesive ball).
Surface tension is caused by cohesion (the attraction of molecules to like molecules). Since the molecules on the surface of the liquid are not surrounded by like molecules on all sides, they are more attracted to their neighbors on the surface.
Applying Newtonian physics to the forces that arise due to surface tension accurately predicts many liquid behaviors that are so commonplace that most people take them for granted. Applying thermodynamics to those same forces further predicts other more subtle liquid behaviors.
Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent-but when referring to energy per unit of area, people use the term surface energy-which is a more general term in the sense that it applies also to solids and not just liquids.
In materials science, surface tension is used for either surface stress or surface free energy.
The molecules constituting a liquid exert attractive forces on each other. A molecule in the interior of the liquid is surrounded by an equal number of neighboring molecules in all directions. Therefore, the net resultant intermolecular force on an interior molecule is zero.
Why do apples float?
Asked by Wiki User
Well, antyhing that is less dense than water will float in water. So knowing this we can assume that an apple is less dense than water.
How many types of turbines?
Asked by Wiki User
three types of combustion chamber are used in gas turbine engine
1) Can type.
1.1 single can ; this again can be of two type a) straight through design b)reverse flow design
1.2 multiple can
2) tubo-annular (can-annular)
3) annular
How deep will a vacuum pump water from?
Asked by Wiki User
i believe the question should be stated as "How high can a pump pull liquid when mounted above the liquid source". an old pump adage is that a pump doesn't suck. sounds dumb, but it refers to the necessity of having a positive pressure at the suction of the pump greater than the required net positive pressure req'd by the pump. NPSHa must be greater than NPSHr. in any system open to atmosphere the surface of the fluid will have 14.7psi (at sea level) X 2.31 ft/psi, or roughly 34' of head, or NPSHa, available. the manufacturers performance curves will show the NPSHr of the pump at any given flow for a given impeller trim. by subtracting this NPSHr from the calculated surface pressure you can arrive at a general maximum lift that the pump can run at. there will also be line friction losses that will reduce this height, and typically we subtract another 2-3' for a fudge factor as you would not want to run on the ragged edge. so, a pump with an NPSHr of 8' would be able to lift cold water approx 22' before cavitating. getting it primed is another issue, and having said all this, there is a type of centrifugal that can successfully trick this seemingly rigid restriction on lift. the typical home commercial jet pump can lift from many times this limited depth by taking a portion of the high pressure discharge and sending it down a separate pipe and into the suction pipe. this effectively increases the suction pressure and allows this type of pump to lift from quite a depth. a really neat way around having to install a down-hole pump submersible. of course the type of pump, what you are pumping, temperature, vapor pressure, specific gravity, and viscosity will all affect the height that a pump can lift a fluid.
If the question is ' at what height we can place the suction side of pump from the water level from where it is pulled up', then if we are not considering the NPSH (which is not practical of course) , then i think that the maximum height of the suction side will be the height which will balance the pressure which is on the water level below from where it is pumped. If the pressure there is atmospheric pressure (at the water level below suction side)then maximum height of water rising is 10.3 m around(will vary according to the fluid being pumped). Above it water will not rise whatever vacuum you create though pump.(Its just like in barometer where mercury doesn't rise above 760mm, although there is vacuum above it in the tube. This is because at base of inverted tube of barometer, pressure is balanced). In practical of course the height is much less of course otherwise cavitation will take place when pressure falls below Vapor pressure of the Liquid being pumped.
How does the viscosity of sea water qualitatively vary with temperature?
Asked by Wiki User
between 0 Celsius and 20 Celsius the dynamic viscosity of seawater at 35 g/kg salinity is reported to be 1.88 x 10-3 and 1.08 x 10-3 Pa s. If you calculate the rate of decrease in viscosity with increasing temperature you get -0.04 x 10-3 Pa s per degree.
How many liters is in 2740 milliliters?
Asked by Wiki User
1,000 milliliters = 1.000 liter
2,000 milliliters = 2.000 liters
2,700 milliliters = 2.700 liters
2,740 milliliters = 2.740 liters
2,749 milliliters = 2.749 liters
This bewildering maze of numbers explains why the metric system has not caught on yet
in the USA. It is so much more complicated than, say, 2,740 fluid ounces.
2,740 fluid ounces is equal to simply 21 gallons, 1 quart, 1 pint, and 1/2 cup.
If mercury was replaced by water in a barometer how high a column would correspond to the normal atmospheric pressure?
Asked by Wiki User
The standard atmosphere (symbol: atm) is a unit of pressure and is defined as being precisely equal to 101.325 kPa. It is equivalent to 760 mmHg (torr) or 29.92 inHg. One standard atmosphere is standard pressure used for pneumatic fluid power (ISO R554), and in the aerospace (ISO 2533) and petroleum (ISO 5024) industries.
Go Here: http://en.wikipedia.org/wiki/Atmospheric_pressure
How hydraulic lift uses pascal's law?
Asked by Wiki User
Hydraulic systems use a incompressible fluid, such as oil or water, to transmit forces from one location to another within the fluid. Most aircraft use hydraulics in the braking systems and landing gear. Pneumatic systems use compressible fluid, such as air, in their operation. Some aircraft utilize pneumatic systems for their brakes, landing gear and movement of flaps.
Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container.
A container, as shown below, contains a fluid. There is an increase in pressure as the length of the column of liquid increases, due to the increased mass of the fluid above.
For example, in the figure below, P3 would be the highest value of the three pressure readings, because it has the highest level of fluid above it.
If the above container had an increase in overall pressure, that same added pressure would affect each of the gauges (and the liquid throughout) the same. For example P1, P2, P3 were originally 1, 3, 5 units of pressure, and 5 units of pressure were added to the system, the new readings would be 6, 8, and 10.
Applied to a more complex system below, such as a hydraulic car lift, Pascal's law allows forces to be multiplied. The cylinder on the left shows a cross-section area of 1 square inch, while the cylinder on the right shows a cross-section area of 10 square inches. The cylinder on the left has a weight (force) on 1 pound acting downward on the piston, which lowers the fluid 10 inches. As a result of this force, the piston on the right lifts a 10 pound weight a distance of 1 inch.
The 1 pound load on the 1 square inch area causes an increase in pressure on the fluid in the system. This pressure is distributed equally throughout and acts on every square inch of the 10 square inch area of the large piston. As a result, the larger piston lifts up a 10 pound weight. The larger the cross-section area of the second piston, the larger the mechanical advantage, and the more weight it lifts.
The formulas that relate to this are shown below:P1 = P2(since the pressures are equal throughout).
Since pressure equals force per unit area, then it follows thatF1/A1 = F2/A2
It can be shown by substitution that the values shown above are correct,
1 pound / 1 square inches = 10 pounds / 10 square inches
Because the volume of fluid pushed down on the left side equals the volume of fluid that is lifted up on the right side, the following formula is also true.V1 = V2
by substitution,A1 D1 = A2 D2
- A = cross sectional area
- D = the distance moved
orA1/A2= D2/D1
This system can be thought of as a simple machine (lever), since force is multiplied.The mechanical advantage can be found by rearranging terms in the above equation to
What are the uses and limitations of flow net in fluid mechanics?
Asked by Wiki User
- Can't be applied in the region close to the boundry.
- Can't be applied to sharply converging flow.
- Can't describe wakes.
Can homogeneous mixtures be separated by distillation?
Asked by Wiki User
Certainly. The components just need different boiling points to be separated by distillation.
Does the value of the coefficient of discharge depends on the flow rate?
Asked by Wiki User
coefficient of discharge depends on the state of the machine/system you are using.
if you are using very textured tubes then this number will be higher. if how ever you are using very flexable tubes and fluid at different pressures this can also effect your results as the inflow and outflow may be different, or the cross sectional area of the tubes again chganging the pressure/flow and thus you Cd value
What is rheology most useful for?
Asked by Wiki User
Rheology, as you know, is the study of matter's flow, especially in liquid states. It is very useful in scientific fields, specifically geophysics and physiology.
Why does water evaporates faster at 100 degree Celsius than 200 degree Celsius?
Asked by Wiki User
yes (that didn't answer my question.)
What wave requires a medium?
Asked by Wiki User
Waves that require a medium are called mechanical waves
How do you go about calculating buoyant force?
Asked by Wiki User
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.
What is fluid friction and what is an example of fluid friction?
Asked by Wiki User
Fluid friction occurs between layers within a fluidthat are moving relative to each other.
How is an airplane wing designed to lift the airplane.?
Asked by Wiki User
If straightened out, the top surface of the wing is longer than the bottom one. When air flows over the wing, it must travel faster over the top of the wing so there is less air pressure. higher air pressure on the bottom and lower air pressure on the top= LIFT. The higher the Airspeed the lower the air pressure is called Bernoulli's principle.
