What is Hydraulics: Definition and 78 Discussions

Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concerns gases. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the applied engineering using the properties of fluids. In its fluid power applications, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through some parts of science and most of engineering modules, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry. The principles of hydraulics are in use naturally in the human body within the vascular system and erectile tissue.
Free surface hydraulics is the branch of hydraulics dealing with free surface flow, such as occurring in rivers, canals, lakes, estuaries and seas. Its sub-field open-channel flow studies the flow in open channels.
The word "hydraulics" originates from the Greek word ὑδραυλικός (hydraulikos) which in turn originates from ὕδωρ (hydor, Greek for water) and αὐλός (aulos, meaning pipe).

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  1. Findustry Corp

    Low Viscosity Oil, Tanks, Pressure Relief Valves and Check Valves

    Hi Whoever, I have an idea for a system which would work for my food business but it doesn't exist. The system essentially relies on hydraulics, pressure relief valves and check valves for recirculation upon reached pressure. All tanks/pipes (The entire system) will be prefilled except for 1...
  2. S

    Find the diameter of the piston at certain heights

    I solved for part A by using the equation r2 = sqrt(m2/m1) * r1 im having trouble solving for part B, I know that you would use the equation F1/A1 = F2/A2 + pgh and solve for r2, but when I solved for r2, I got an undefined number. Can someone run me through this question?
  3. doconnor17dan

    Calculations for Hydraulic Jacks lifting a load

    This cylinder is connected by a pipe to the larger diameter jack cylinder on the right where pressure p2 acts on the piston which has an area A2 and is able to lift a load equivalent to the force F2. The piston area of the hand pump cylinder is 2.0 cm2, the piston area of the jack piston is 10.0...
  4. N

    How to design hydraulic system and size cooler

    Hi all, I've started working recently in a new job as an engineer in a lab with a bunch of physicists. A job they've given me is to size a water/glycol chiller (and basically design the hydraulic system i.e. fittings, tubing etc) to cool a bunch of equipment they've got in a few insulated...
  5. T

    Cylinder Force Calculations

    I am trying to calculate the force required to lift/move the beam clockwise from the shown position. I have a force (F1) acting at the end of the beam, 5,000lbs pushing to the left, as shown. What is "Fcyl", or the force required by the cylinder to life the beam with the acting load, and rotate...
  6. C

    Hydraulic Losses Through a Pipe

    I am trying to estimate the pressure loss from a tap to a piece of equipment we are feeding water to. I have the pressure on the 12" ductile line. I have the friction losses in the different pipe sizes (1",1.5", and 2") for the service line. I also have the losses through the 1" meter. The only...
  7. DadoNoah

    Calculating force on a syringe plunger for a viscous fluid?

    I'm currently working on a precise glue/resin dispenser, and I'm trying to derive an equation for the force one must exert on a syringe plunger as a function of the desired flow rate Q, and also accounting for the fluid viscosity and the syringe barrel and needle geometry. I've attached a scan...
  8. Nero

    Project to design and calculate the hydraulics for a deck crane

    Hi, Iam having a really hard time with this university project. The project is to design and calculate the hydraulics for a deck crane. The crane boom must be lifted with one or more cylinders and you want a boom angle from 0 to 80 degrees. Lifting capacity must be 10 ton on 20 m arm at a boom...
  9. KaitD

    How to Apply Bernoulli's Equation to Solve Fluid Hydraulic Homework Problems

    Summary: Currently having issue with fluid hydraulic homework. Only put down Bernoulli’s equation on my paper [Moderator: moved from a technical forum, no template.]
  10. F

    Hydraulics help please -- Energy loss in a long pipeline

    Homework Statement Homework Equations y1 + P1/##\gamma##+v1/2g=y2 + P2/##\gamma##+v2/2g+hL The Attempt at a Solution I used the above equation and assumed that P1=0 and both velocity heads are equal. Is that valid? However I did not need to use the geometry of the pipe so I think I am doing...
  11. F

    Is Bernoulli's Equation Applicable for Finding Pressure in Hydraulics Problems?

    Homework Statement Homework Equations y1+P1/##\gamma##+##\alpha##v12/2g = y2+P2/##\gamma##+##\alpha##v22/2g + hL The Attempt at a Solution so it gives me pressure at p2 but not p1. I tried using Bernoulli's equation to find p1 i did plugged into energy equation above and got an answer but...
  12. Z

    Equilibrium of pistons with different radii (Hydraulics)

    Homework Statement [/B] Homework Equations Force exerted by liquids F=h.d.g.A The Attempt at a Solution
  13. fando1234

    Lifting an elephant with hydraulics

    Hey guys, I'm a super amateur at physics, but I occasionally like to calculate random problems that pop into my head. Today I was thinking about pascal and hydraulics, and wondered if I could devise a (hypothetical) hydraulic system that would allow my weight to lift an elephant. I want to...
  14. F

    Calculating Best Hydraulic Section for Composite Channel - Flow Rate 6.5(m^3/s)

    Homework Statement Determine the depth of the flow of channel if the best hydraulic channel is needd for composite channel in figure to convey flow rate of 6.5(m^3/s) , Manning coefficient n on bed slope are 0.015 and 0.0015 respectively . Homework EquationsThe Attempt at a Solution I assume...
  15. E

    Is my scissor lift's hydraulic system in need of a major service?

    Hello! I have a scissor lift which was http://www.pentalift.com/lift-tables/scissor-lifts&multi-stage.php in 2002. It's been working perfectly until last week. Last week when I tried to lift it with 3 people on it, it didn't go up entirely. We used to lift up to 6 people on it, but now it's not...
  16. Rod Alexei

    What do you guys think about Dynamic Tidal Power?

    I am a 16 year old trying to make a research paper about it for my science high school. I'd like to study how it works and whether it can be applicable to Busan, South Korea. Thank you :)
  17. CivilSigma

    Derivative in mass flow rate equation - Hydrology

    Hello, I am working with the mass flow rate equation which is:$$\frac{d \dot{m}}{dt}=\dot{m}_{in}-\dot{m}_{out}$$ To determine the change of the height of water in a reservoir. Assuming m_in = 10 and m_out = sqrt(20h), then : $$\frac{d (\rho \cdot Q) }{dt}=\rho \cdot Q_{in} - \rho\cdot...
  18. C

    Forces Due to Static Fluids

    Homework Statement Find height (h) of the water level which can result in failure of dam by tipping it over due to water pressure at U/S of dam. Also draw the free body diagram. Density of water to be = 1000 kg/m^3 and its specific weight=62.4 lb/ft^3 Hints: The specific weight of concrete is...
  19. T

    I Calculate Minor Losses due to Flow Geometry Alone

    Hi does anyone know a way to calculate the Minor losses related just to flow Geometry isolated from Major frictional losses, all the k tables I can find combine the frictional losses with the geometry losses eg see below blurb from but I was hoping to obtain a first principles formula that...
  20. E

    Passive Hydraulic System to Transmit Mechanical Power

    Hi All, I am trying to displace mechanical power using a hydraulic system with the fluid as the energy conduit. I will be using two cylinders with a connecting pipe, so when I push one down the other rises. This video illustrates well what I am going for in terms of hydraulic topology. My...
  21. M

    Corresponding Pressure gradient with flow velocity

    I have some questions concerning hydraulic engineering. I'm currently working an simulating laminar flow. This laminar flow is induced by a pressure gradient. The assumed length is 1 meter, therefore the pressure gradient is equal to the actual pressure in reference with zero. What are typical...
  22. M

    Pressure drop across a valve in hydraulics

    Hello, I read something about the pressure drop across a valve and it was specified this is a singular pressure drop equivalent to K*U²/g (Borda formula). My question is, can we used the Bernouilli formula for a permanant incompressible flow to determine the flow rate function of the pressure...
  23. J

    Hydraulics, venturi flume questions

    Homework Statement A venturi flume is formed in a horizontal rectangular channel 1.2m wide by locally constricting the channel to a width of 0.9m and raising the floor level through the constriction by a height of 0.2m. If the flow is 0.45 m3/s and a hydraulic jump forms downstream, calculate...
  24. M

    Useful book to learn hydraulics and pneumatics

    Hello, I'm looking for some books which can help me to learn about hydraulic, pneumatic and fluid mechanics. Can someone advise me a good one ? Thank you !
  25. S

    Thermal Hydraulics: Solving a PWR Problem

    Hi guys, I'm a starter in Nuclear thermal hydraulics course, and I'm having a hard time in solving this problem:1. Consider a PWR operating at the thermal power of 1893MW. It contains 193 fuel assemblies, each consisting of 204 UO2 fuel rods 1cm in diameter. Using the equation...
  26. I

    Force require to move water through a pipe?

    I'm writing the third in a series of Young Adult Sci-Fi/Fantasy novels, and I'm trying to calculate how much force would be required in the following: Imagine a pipe that is 1.25 centimeters in diameter and 3000 meters long. The pipe lies perfectly flat, but a meter of the pipe at each end is...
  27. K

    Hydraulic motor torque for a home-built flight simulator

    I am constructing a home built flight simulator and am using hydraulic motors with a arm attached to the motor spindle for movement. I need to know how much torque I would need in the motor to lift 1000 lbs. Also I need to know how fast the motor should be to move the weight 1 foot in 2 seconds...
  28. 2

    Hydrostatics: What remains the same in a fluid?

    I am looking into hydrostatics, but am now very confused about what has to remain constant in an incompressible fluid. I initially thought that pressure has to be the same all throughout the fluid, and that this is the reason why you can use water or oil when raising a car- you apply a small...
  29. J

    Can Hydraulic Circuits Transport Energy Without Compressible Oil?

    How can energy be transported in a hydraulic circuit? The volume of oil is nearly incompressible. Therefor energy can not be transported in the form of potential (inner) energy of the oil.
  30. M

    Can I use one hydraulic pump for two identical motors?

    Hello I need guidance on selection of a hydraulic motor. Motor would be used to drive the wheel of a vehicle. Motor needs to generate a torque of 18.3Nm in order to overcome static friction and move the vehicle. And the motor needs to be small enough to be coupled with the tire (see the picture)...
  31. M

    Hydraulics and Hydraulic Machines

    Hi, Any good and detailed book on hydraulics and hydraulic machines ? Much grateful Need to cover topics on Water Turbine, Flow through Pipes and Head Losses with detail derivations.
  32. V

    Friends I on fluid machanics

    Dear Friends, I need some ideas on a problem I am facing at work. I have attached a sheet with has a rough picture of scenario. I urge you to please keep open the picture while reading my problem. Problem:- There is a small wall in a water stream. Due to the small wall the water stream upside of...
  33. J

    Hydraulics and pressure problem

    Homework Statement The hydraulic system is this: It has two stamps (Unsure of how I am to translate that word). Basically it is the plate on which we apply pressure. You apply pressure on one of them, the other goes up. The question is: How high will the big stamp move upwards when the small...
  34. P

    Question about hydraulics and mechanics

    I was just wondering if any Mechanical Engineers could answer me this. You know how cranes and prototype robotic limbs move but at a really slow pace? And when a crane closes its arm, it doesn't do it quickly but really slowly. In the future, will we be able to overcome that limitation and allow...
  35. T

    Basic Hydraulics: Flow, Pressure, Force, Area, Energy

    Hello, I am trying to get a grip on the basic relationships in hydraulics. I do not need the advanced math and engineering, compensation for frictional losses, and fluid viscosity and turbulence effects. Just a good basic understanding. The first concept that comes to mind is the concept of...
  36. L

    Very basic phisics, hydraulics and weights, wrong diagram?

    Hej Guys, I am just wondering. See the picture. If I put 5kg on the right the water lever increases and the new water level on the left should be as much higher as 5kg volume of water. Its so obvious isn't it? So if it is obvious can you please tell me that why it is possible that in a...
  37. C

    Hydraulics Engineering: Why does Velocity stay the same when Roughness

    I used the E.P.A.'s EPAnet program to run a network analysis. I noticed that if I change the roughness of the main pipe connecting the reservoir with the first junction, the pressures do change on the network but all the velocities are same! Also if I do change the roughness on an internal...
  38. S

    Gland and Seal for Brake Hydraulics Question

    Greetings, I'd like to solicit assistance relative to a brake hydraulic system. I am rebuilding a vintage system that contains a pressure differential unit. The unit contains a dynamic piston with seals in a fixed bore. The seals are intended to keep fluid outboard of them in the bore. I...
  39. R

    I want to study Hydraulics I need good books

    it's civil engineering hydraulics, and I want to be good at it, I am in need of some good textbooks and problems book anyone out there who knows?
  40. M

    Engineering hydraulics question

    Homework Statement Points A and B are separated by 3000 ft of new 6-in schedule-40 steel pipe. 800 gpm of 60 deg F of water flow from point A to point B. Point B is 60 ft above point A. What must be the pressure at Point A if the pressure at B must be 50 psig? Homework Equations...
  41. J

    Engineering How important is Fluid Mechanics and Hydraulics to Civil Engineers?

    I know the main focus of Civil Engineers are the strength of the structures. I also know that Fluid Mechanics and Hydraulics are important in designing dams or other structures related to fluid. But what about to Building structures? How is it important?
  42. T

    Solve this algebraic equation for 'D' (Hydraulics)

    Never mind.
  43. J

    Hydraulics problem - calculate pressure at different points

    Homework Statement Hey, stuck on this question in my hydraulics course: Question involves lubricating oil pumped around a large piece of machinery. Density of oil = 810 km/m3. Viscosity = 0.01 kg/m.s throughout the system. Flow rate is 0.140 Litres/sec Pipe diameter = 3mm Pressure...
  44. Femme_physics

    Good resource for gifs and animations of hydraulics?

    I wouldn't have asked unless I really needed and couldn't find. Google only shows me images, and I even tried searching in gifs-specific websites to no-avail. Perhaps you guys already know some resources, so I'll stop wasting so much time with search engines?
  45. Femme_physics

    Hydraulics - System curve VS pump curve

    http://img849.imageshack.us/img849/9018/curvess.jpg So pump curve, as flow increases, pressure drops. For the system curve, it's the other way around. How come? How come the pump disobeys the way the system is supposed to behave? The pump is a part of the system, and in the physical world...
  46. Femme_physics

    Hydraulics - Problem finding pressure

    Homework Statement http://img37.imageshack.us/img37/638/pumpyu.jpg (the pump is between 1 and 2) D1 = 300mm [diameter of pipe 1] D2 = 250mm [diameter of pipe 2] k(pressure lost due to valve) = 7 k(pressure lost due to 90 degrees pipe angle change) = 0.9 K (pressure lost due to entrance to a...
  47. W

    Hydraulics, Flow rate from Bernoulli Equation

    Homework Statement Flow rate in Venturi meter of Petrol (SG 0.85). Diam1 - 0.2m Diam2 - 0.15m Height Diff in manometer of Mercury (SG 13.6) 0.012m, so Δp= 13600 x 9.81 x 0.012 = 1601? Cd = 0.98 Homework Equations Bernoulli, p/ρg + U2/2g + Z U=Q/A The Attempt at a...
  48. E

    Static hydraulics, calculate water depth

    Homework Statement Refer to Figure 3. A steel box (250 mm x 250 mm x 250 mm) is placed at the bottom of a tank. If the pressure on the top surface is 10000 Pa, what is the water depth in the tank? Answer a. 1019 mm b. 251.02 mm c. 1269 mm water density: 1000 kg/m3 gravity...
  49. M

    [Basic Hydraulics] The Pitot Tube/Manometers

    Homework Statement Determine the flow rate, Q. Ignore energy losses. Given: D1 = 100 mm D2 = 75 mm Fluid in the pipe is water. Fluid in the metre is mercury. S.G. of Mercury is ~13.6. The difference in height of the mecury columns is 80mm. Diagram is below. Homework...
  50. M

    Hydraulic Entrance Loss Benefits: Fluid Flow 3K US GPM

    I am trying to determine the entrance loss benefits of changing the entrance conditions from water run-off (gravity flow) from a smooth (steel plate) surface into a rectangular channel box that is under induced suction. Currently, I believe that I am restricting water removal-flow through a...
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