# What is Hydraulic: Definition and 338 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. ### Automotive Poor Man's Hydrostatic drive: power steering pump as motor?

I'm toying with the idea of building a UTV/ATV using parts from an old John Deere 210 lawn tractor. The main design problem I have is I need to reconfigure the motor relative to the transaxle. The transaxle is a 4 speed Peerless 2300 with reverse. Because of the shift arm location, I have to...
2. ### Simple question regarding weight flow rate and specific gravity

i’m studying my textbook in hydraulics and i’d like to know the reason why specific gravity is used in one of the problems. it’s a pretty simple problem and i understood it mostly except why specific gravity is multiplied to 9810 (the unit weight of water). if the SG is given in the problem, is...
3. ### I Why does the end of the fracture have a branch? (Fracking)

Hello, I have seen some pictures about hydraulic fracturing, which is injecting water into the ground under high pressure, and when people draw the schematic, it looks like this I am wondering why the fracture will be branched. Thanks!
4. ### Better model for a hydraulic motor

Hi all, We are doing some work with Eaton 760 series fixed displacement hydraulic motors and are looking for a better mathematical model for the torque output. Does anyone know a good place to look? Something that includes differential pressure and temperature would be ideal. Thanks Ed
5. ### Flow in and out of hydraulic motor

Hey all, It is possible I am over complicating this, but is the flow in and out of a hydraulic motor with an electrical load the same? Assuming no losses. Scenario is a hydraulic piston (moving by some external force), driving a bi-directional hydraulic motor which itself is driving an electric...
6. ### Static hydraulic pressure in a pipe

My Question: Two pipes filled with water and caped at one end, they have the same diameter, but different lengths. One pipe is 10 feet long and the other pipe is 1,000 feet long. At the other end of both pipes a piston applies an equal amount of pressure on the water in the pipes...
7. ### 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...
8. ### Hydraulic lifting force of this arrangement of pipes

Hello All, :) Please see the picture , input force F1 and area A1 and second area A2 are all same for 3 cases . in case 2 and 3 , red open outline represents a free-to-move , ie , "T" piece move upward for the 1st case , output force F2 should be F2=A2/A1 x F1 , by pascal's principle ...
9. ### B Can the output forces for F3 and F4 be the same as F2 in hydraulic lifting?

Hello All, pls see picture , input force F1 and area A1 and second area A2 are all same for 3 cases for the 1st case , output force F2 should be F2=A2/A1 x F1 , by pascal's principle , what about output forces of F3 and F4 ? can be same as F2 ? how i calculate them ? thanks
10. ### Hydraulic Liftgate: Find Optimal Cylinder for 90° Rotation

Hello everyone and thanks for any and all feedback! I am looking for help with a hydraulic system for a liftgate conveyor I will be installing for a customer. The conveyor is 10" in length and 3' wide but the liftgate portion is only 7' long. The approx. weight of the 7' section 500lbs. My...
11. ### Calculating Hydraulic Jump with Unknown Cross Sectional Area: Help Needed

I have 90% of this done. When i looked in my manual i noticed an odd jump they made and i don't get why. that is where i need the help V1(b1h1) = V1(b2h2) Im solving for h2. What i can't figure out is what to use for the base measurement of the cross section of the water. i have no idea how...
12. ### Problem with different hydraulic connection sizes on CNC machines

Hello guys, I am supplying a Venturi Vac to my clients which is installed directly on their CNC Machine Coolant Pumps (photo attached). This is done by introducing a Tee connection on the discharge end of the pump as shown. The straight line of the tee is connected to the hydraulic coolant...
13. ### A Hydraulic jumps: Why do they occur when/where they do?

Hi guys, I've been doing some light reading on hydraulic jumps. For example: So I've been through the basics, super critical to sub ciritcal etc: https://en.wikipedia.org/wiki/Hydraulic_jump So far I understand that the jump occurs at the two points either side of the critical depth, like we...
14. ### Hammer press equivalent to 6 Ton hydraulic press

i need a help, this is my first post in this platform, actually few year ago I perform a forging operation in a 6 Ton forging press but now i have 3 Ton hammer press, can i use that press to make that product. is there any calculation to find out equivalent hammer press of a forging press
15. ### How to calculate distance in a hydraulic press when you have 2 pistons

Hello!a) Now here I've simply though "logically" and drew a litle sketch and I think the answer should be 0N.No calculation needed I'd pressume (if needed I don't know how to do it) b) Here I've used the fact that $$p1 = \frac{F1}{A1} = \frac{F2}{A2}$$ For the surface I just went with ## A...
16. ### Steering Effort on Sailboat w/ Hydraulic Rudder Control

Greetings to everyone, Recently I bought sailboat with rudder which is actuated by hydraulic oil by cylnder and pump at steering wheel. I have been trying to calculate steering effort(feedback) on my hydraulic operated sailboat if I change my current cylnder,but nusucessfully. Problem is that...
17. ### I How viscous forces affect force transmission in hydraulic systems.

Hi everyone, I have a question that I am struggling and need your help. So I am working on a project which is essentially two syringes, A & B, with different cross-sectional areas, A1 & A2, connected via a tube filled with water. If we assume loss-less system, Pascal's law, the input force...
18. ### Calculating Valve Size With a Hydraulic Accumulator

Hello, Hope everyone is doing well. I have a personal project I am working on and am trying to figure out the nature of the hydraulic system. I want to size a valve to the system properly and have been reading a lot about the Cv value. I don't fully understand how to implement this value into...
19. ### Selecting hydraulic motors and a pump for hydrostatic transmission

So I'm trying to make a GoKart that utilizes a hydraulic drive for the front two wheels and a mechanical driveshaft for the back two wheels but my main questions are selecting the motors and pumps. I just want to clarify a few things since I'm not sure if I did my math right. The max RPM for...
20. ### Calculating Hydraulic Press Pressure on a Skateboard :)

Hi all, I wonder if someone can help me with a calculation/estimation? I have recently built a skateboard press to...press skateboards! My question is, how do I calculate how much pressure is being applied to the skateboard? Most presses are steel, however, not having any metal working skills...
21. ### "KICK" force exerted from a hydraulic cylinder

Hello,I am building a press that will squeeze hot steel ,back off .5"push hot steel in further and repeat.The cylinder is 4" bore , 1.375"rod and travel is 8" (the majority of squeeze will be at 5"of extension)at a max of 2500PSI. my question is when putting @15 tons straight down what will the...
22. ### Hydraulic Car Ramps...... need to make them go up and down

I currently jack up the end of the ramps using the channel frame and a 3 1/2 ton jack, because of the height of the channel frame I have to have it sitting quite far back under the car for clearance when the ramp is lowered down to drive off. I have to push the jack a long way under the car to...
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### B Hydraulic resistor as a constriction in a pipe

Earlier I was trying to explain to one of my siblings why current is constant in a series connection (invoking that if it weren't we would have an accumulation of charge, etc.), however to give a more intuitive picture I tried to describe the hydraulic model of electric circuits, representing a...
24. ### Hydraulic pressure/flow -- friction loss question

Flow delivered by a pipe can be calculated from input pressure, inlet geometry, pipe length, and a flow coefficient related to pipe cross-section, shape, and roughness. If we create an example of a pipe attached at the bottom of a self-refilling standpipe, which automatically supplies a...
25. ### Can you help me find the right hydraulic valve?

Hi I'm a novice when it comes to hydraulics but I want to be able to make use of it in future projects. I thought building a small scale excavator might be a fun project to start with. However I'm a bit confused when it comes to the valves that will control the different motions. From what I've...
26. ### Dialysate flow rate when pulling through a jug

Friendly argument at work (both non physics majors) with what tube would fill up faster with a flow rate (siphon like) that remains the same through two different diameter tubes. The dialysate jug is open to atm pressure. One tube is about .5 inches in diameter and the other is .25. We were...
27. ### Water Tank Refilling via Hydraulic Water Pumping System

Based on my understanding, Top Tank Refilling Advantage: Atmospheric Pressure Disadvantage: High Head (Requires more distance, thus more Work since W = f x d) Bottom Tank Refilling Advantage: Low Head Disadvantage: High Static Pressure (Requires more Force, thus more Work since W = f x d)...
28. ### Frequency response - Hydraulic network

Hello everyone, i have a measured signal of a high pressure oscillation in a hydraulic network. Performing a FFT of said signal shows two dominant frequencies, a and b. After performing a linear analysis of the hydraulic network i found out that the network has two eigenvalues at those...
29. ### Wood/Glass/Metal Wooden hydraulic mechanical arm

Yesterday, I found a device in the recycle bin of our school’s art classroom. It’s a broken wooden hydraulic mech arm someone built a couple years ago. After some fixing and filling the syringes with water again, this is how it looks now: Here’s a video of it working: I am aware of...
30. ### Burst valve obligation on hydraulic lifting cylinder

Hi everyone, I heard that there is a regulation\obligation that requires burst valve installation on lifting hydraulic cylinders. My questions are: Is this requirement apply to all lifting appliances or just appliances involve with personel lifting ? Is this requirement apply to forklift...
31. ### Modeling Hydraulic Brake Behavior

Summary: Relation between deformed foil and friction force Good morning everyone, i have a small leaf or steel that is bent from one side by a Pressure of many bars. in front of the leaf there's a rotating disk, separated by the leaf by a small gap. this leaf, as it deforms, wins the gaps and...
32. ### Question about hydraulic jump assumptions

Sorry for the poor image... A better picture can be viewed here https://www.dropbox.com/s/uyi01l27vu2fwyw/96.png?dl=0 I don't understand the assumption in the red box... If I don't ignore the atmospheric pressure, F_1 = integrate from 0 to h_1 (ρg(h_1-z)+p_a)dz = 1/2 ρgh_1^2 + p_a*h_1, similarly...
33. ### Hydraulic Oscillating Ram Pump

How can I get the Input Torque required to pump the double-acting cylinders with the following specifications below? Ram Working Pressure = 2 bars Ram ID = 100 mm. Ram Stroke = 1,000 mm.
34. ### Increasing Torque with Gerotor Design: Lengthening, Diameter, and Series

How do you increase torque in gerotor design other than increasing flow. Will lengthening it increase torque? Will increasing diameter increase torque? What about running 2 or 3 in series?
35. ### Hydraulic winch torque questions

I am designing a winch to put behind my tractor, and I am going to power it using a hydraulic motor. My tractor puts out about 1000 PSI of hydraulic pressure, and the hydraulic motor I want to use is 9.8 cubic inches per revolution. I calculated that at those specs, the hydraulic motor will...
36. ### Hydraulic Modeling of Central Heating Network

In this task of mine, I need to develop a tool/software to carry out (dynamic) hydraulic analysis of a central heating network, formed with supply and return pipes so forming a multi-parallel loops in a closed circuit, as can be seen in the below picture. Can anyone suggest me some references...
37. ### Hydraulic machines (Francis turbine)

When my teacher was explaining about impulse-reaction inward Radial flow (Francis) turbine, he said that as the water moves from inlet to outlet tip of the blade, pressure energy of the water is used to do work and pressure reduces(reaction effect).Then he added that due to this decrease in...
38. ### Calculation of Velocity and Shear rate in rectangular channel

Hi everyone, I would like to know the formula for calculation of velocity and shear rate in my rectangular fluid channel. Here are the important values regarding my rectangular channel. W= 2.5 mm, H=3 mm, L=35 mm. Fluid: Diluted Bacterial suspension derived from wastewater. Flow rate: 0.125...
39. ### Hydraulic head as a function of flow rate

Hello! 1. Homework Statement Symbols and variables: ##\dot{V}## : flow rate ##H## : Hydraulic head ##g = 9.81 \frac{N}{kg}## ##P_{atmosphere} = 101325Pa## ##\rho = 1000\frac{kg}{m^3}## I am given a piping system, with serie and parallel pipes, they start from one point and go back into one...
40. ### RTG crane -- hydraulic motor and linkage design to turn these wheels

Hi all I would like to ask your professional guide in designing a hydraulic system. I attached a file, showing sketch of the RTG crane wheel structure. Here are the conditions: 1. The red-line is the hydraulic cylinder with "X" as the fix point. 2. The hydraulic cylinder will stroke out from...
41. ### I need a large hydraulic motor

Hi Would someone please be able to help? I am based in the UK We need a large hydraulic motor... 6000 metres of torque with a speed of 1800 or 1500 RPM If two motors were in-line would this achieve our goal? Many thanks for your interest. Chris
42. ### Force Calculation -- Hydraulic cylinder and a rotating arm

Hi There, Long time reader, first time poster.. I hope someone out there can help me. I'm designing an add-on to an existing piece of equipment and I'm unsure of how to calculate the resultant force output from a hydraulic cylinder. On a straight push, the chosen hydraulic cylinder has an...
43. ### Hydraulic Head Loss (minor) loss coefficient References?

Hi all, Quick question: What do you guys use as your reference for minor head loss coefficients (k). I'm sure those with more experience have their own database/excels of k values found over the years. I have been personally using a combination of my Hydraulic Engineering Textbook and Google...
44. ### Operation of this hydraulic circuit?

Can anyone explain the operation of this circuit? I'm finding it hard to understand hydraulic circuits, like where is the source of fluid coming from? I know what all the components are and what they do. It's just trying to understand how it actually operates.
45. ### How to calculate the pressure on a piston in a damper system?

Hello all, I'm trying to calculate the pressures exerted back on a piston by a working hydraulic fluid in a damper system. I've attached a drawing of the system and the equations I'm using. Essentially the piston motion is restricted by flow through an orifice. I have data for the flow rates...
46. ### Wind Turbine Hydraulic to Electrical Conversion

As a hobby for the last couple of years, I've been designing various theoretical wave and wind generator devices. One of the primary criteria is that the electrical power generation components have to be easily accessible. For wave power, electrical power generation has to be on shore not in...
47. ### Hydraulic jack - Pascal's principle

Homework Statement Homework Equations P1=P2 P=F/A F=PA F1/A1=F2/A2 F2 = F1(A2/A1) F2 = W(A2/A1) W=mg W=F*d The Attempt at a Solution A1= pi/4 * d2 = pi/4 * (0.15)2 = 0.0177m2 A2 = pi/4 * d2 = pi/4 * (0.05)2 = 0.00196m2 P1=P2 P=F/A F=PA F1/A1=F2/A2 F2 = F1(A2/A1) F2 = W(A2/A1)...
48. ### PID tuning of hydraulic drives with high inertia

Hi there. I have a question about the tuning of a PID (PI) controller in hydraulic drive trains with high inertia. I have a system with a 100kW hydraulic motor with an installed on its shaft encoder. That is how I am getting feedback from it. Not surprisingly I have a controller for acquisition...
49. ### Motor driven hydraulic cylinder design

I am trying to design a mechanism which has a hydraulic cylinder driven by a step motor. The motor shaft is connected to the hydraulic cylinder piston via two rods of lengths r and L as shown in the below figure. I want the cylinder's piston to be driven at constant velocity v, so I am trying to...
50. T

### What is the significance of lag time in a hydrograph?

Homework Statement Lag time in hydrograph means teh time of center of rainfall to center of hydrograph , according to my book . Homework EquationsThe Attempt at a Solution Since lag time can be understood by the time taken for the water to reach river , contributing to max discharge ... So ...