# Tag Info

22

The 'steps' are called weirs, and they are used for a number of flow control reasons in rivers. In the case of the images you posted, they are probably being used to stabilize the grade (slope) of the river. When used for this application they are sometimes called drop structures which "pass water to a lower elevation while controlling the energy and ...

20

The two photos in the post show the same structure: Pulteney Weir, downstream of Pulteney Bridge on the River Avon in Bath. The shot of the "Seine" in Les Miserables was filmed on location in Bath. Pulteney Weir was designed by architect Neville Conder, and built between 1968 and 1972. It's one component of the Bath Flood Prevention Scheme, which was ...

5

Ultrasound partially reflects when it encounters a medium with different acoustic impedance. It behaves like light and obeys Fresnel equations. If the angle of incidence is smaller than the total internal reflection angle, then part of the ultrasound beam will go forward (with some refraction) and part will reflect back from the interface between the media....

4

I am afraid the question you are asking might not even be a valid question. This is because of the correlation between the Reynolds-Number ($Re$) and the occurrence of turbulence. $Re$ is not a fluid mechanic switch (turning turbulence on and off) it is more a parameter which allows for describing and clustering flow phenomena. $Re$ describes the ratio ...

4

The problem you have is more complicated than you think. Any industry that deals with the storage and movement of granulated/powdered materials has to deal with this and most have unique solutions. You need to look at the principles of hopper design. Some of the things that affect any design will be: The angle of repose of the material you intend to use. ...

3

I suppose you need some kind of powder doser or volumetric feeder It might work on measuring time. Very easy principle, you need valve (maybe solenoid valve or for some sort of flap door) and timer switch. Mark volumes on your container, measure time needed for filling each volume for each spice you need and program your valve. You could use Arduino to ...

3

You are correct, the Reynolds number is what determines whether a flow is laminar or turbulent. The formula for the Reynolds number is $$Re = \frac{\rho vL}{\mu}$$ $\rho$ is the density, $v$ is the velocity of the flow, $\mu$ is the dynamic viscosity of the fluid, and $L$ is the characteristic length associated with the flow. The first three figures can ...

3

Conical hopper with gate control.

3

Here is a reference from RoyMech, see section under "Orifice Flow Meter". The setup has the orifice placed in a pipe. Below is a similar, perhaps simpler, expression, from Jobson 1955, part of the way between equations (4) and (5) of that paper. (The paper is really about incompressible flow, this is just a warmup for the author). $$\dot{m} = {{\... 2 Assuming you are wanting to minimize turbulence in the region of the pump, you would probably need to use flow straighteners somewhere upstream of the pump. You would have to study the optimal diameter and length of the straighteners. MIT simply used drinking straws to do this in a wind tunnel. Here are a couple of the more well known papers on the ... 2 In wind tunnels usually meshes and/or honeycombs are used to reduce turbulence. However, to really achieve low turbulence it's probably not enough to add a single component to your facility. I rather suspect you need to evaluate the overall design. Some kind of diffusors at the pipe end(s) might be helpful. If you look at the flow behind bridge pillars, you ... 2 You will probably need to install a check valve (or manual valve) to prevent the backflow, and rebuild the pump heads periodically. Over time, the gears wear down and small gaps form. This both leads to reverse flow when the pump is off and reduces the liquid flow rate for a given pump speed. I used to work at a plant that used gear pumps that look similar ... 2 The number isn't as important as total surface area of the holes - it doesn't need to be greater than the can opening for the remaining pressure resistance to be entirely negligible. Decision on the number should be a trade-off between uniform distribution of the load and possibility of having the holes sealed by dirt or whatever contaminants could be ... 2 As long as you are not sending data, any light input in one end should be detectable with a color filter covered light sensor at the other end. Example: green film for a green led/laser. Light at the sensor means the beam is not blocked, no light means it is blocked. No fancy modulation should be necessary unless you are trying to filter out similar ... 2 Google "Rankine cycle". The boiler operates at an elevated pressure (sometimes several atmospheres). But because steam at a given pressure is many times bigger than liquid water at the same pressure, the energy required to pump water into the boiler is considerably less than the energy obtained from using that water (as steam) to power the extracting ... 2 I'm an electrical engineer so this problem looks to me like an RC (resistor-capacitor) discharge. In the case of a resistor discharging a capacitor the time constant is given by τ = RC. In your case C represents the tank capacity and R is your R1, the resistance to flow. Figure 1. The top curve shows the capacitor voltage which is analogous to liquid level ... 2 Yes. The range of airflow required is established by the swept volume of the engine and the max rpm. That will then define the pressure drop and venturi needed - which is often controlled by a moving piston to give a larger orifice for higher airflow. Based on the air/fuel ratio the orifice for supplying the fuel can be designed and some (most) carbs use a ... 2 One basic way is to adjust the valves, the dry ones fully open and the ones bleeding all the pressure just slightly open, or even restricted permanently by a smaller size bushing just before the valve. In conjunction with that, you can install a water tank between the pump and your network with an adequate head and a hydraulic actuator to stop the tank's ... 2 The most precise way to control flow is with valves/flow regulator. The main problem is the cost. Although, its a very basic component and its not too costly if you have too many outlets the cost will pile up. Even if you had matching orifices, you might have issues with the pressure drop inside the pipes and corners. Another way to control the flow would ... 2 If you know the external diameter and orifice diameter, From Wikipedia the orifice plate equation :$$q_m =\frac{ C_d}{\sqrt{1-\beta^4}}\epsilon\frac{\pi}{4} d^2 \sqrt{2\Delta p \cdot \rho_1}  where: $C_{d}$ = coefficient of discharge, dimensionless, typically between 0.6 and 0.85, depending on the orifice geometry and tappings $\beta$ = diameter ...

2

Flow rate is directly proportional to the square root of pressure. So for any given orifice, all else being equal, $\frac{GPM}{\sqrt{PSI}}$ is constant. Technically PSI here is the pressure difference across the orifice, but with no backpressure only the input pressure matters. For an orifice rated 1.8 GPM at 90 PSI, $\frac{GPM}{\sqrt{PSI}} = 0.1897$. To ...

1

If the flow rate is 5ml/min, and you want to know how long a tube it will take 1 min to pass through, you’re effectively asking how long a tube contains 5ml. Volume of a cylinder is $\pi*r^2*h$. 5ml = 5000mm^3. Pi*r^2 = Pi*2mm^2 = 4pi mm^2 Your length therefore is 5000/4pi or around 400mm.

1

You made a small mistake if we are going to use Poiseuille's law. $Q_{final}= Q_{initial}\Delta r^4 \rightarrow \Delta Q =(\frac{r_{final}}{r_{itial}})^4$ Plugging your numbers, $Q_{final}=Q_{initial} (0.75/0.25)^4 \\ =Q_{initial}3^4=81Q_{initial}$

1

The flow meter needs to be installed such that it is always under pressure (in normal operation). That is it should be after the regulator but before the on/off valve. That way you will get no surge of gas entering an empty pipe and pushing up the float. It is quite a common problem.

1

This is a challenging measurement. In my opinion best done with a very good balance. Fully shielded from thermals and vibration, obviously. Use a small container with small opening diameter to limit evap to what will hopefully be under 10% of the final measurement (and we will correct for it more later). A clean 2mL glass bottle is good. Fill bottle halfway, ...

1

By knowing the volume flow rate of a gas , you can also find the mass passing through a cross section area for certain thermodynamic conditions.

1

The Objective of this experiment is by the way to investigate the linearity and hysteresis of the flow sensor. The key word here is hysteresis: the output of the sensor at the same flow rate might not the same depending on whether you are in the increasing or decreasing output direction. This is why you are being asked to test in both directions. Check ...

1

Drip irrigation parts cost about five cents a piece. They come in fractional gallons per hour at 25 psi. So pump the water into the tank from the bucket via a drip head, and use a simple float valve to regulate the outflow. First thought is a carb float. Toilet float might work as well.

1

Yes, you definitely can do that. There are small filler pumps that will automatically kick into power when the water falls below the present level and the floater activates the pump. So you can have the discharge drip continuously but the infill intermittently, automatically. And by putting a call control valve on the drain path, you control the whole ...

1

Saturated flow through sediments is governed by Darcy's Law, which relates the pressure drop across the porous medium to the permeability of the medium to calculate the fluid flow rate. The fluid viscosity affects the relationship but is usually assumed to be constant in groundwater studies. That may or may not be the case for your coffee (e.g. if the ...

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