# 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 ...

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

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

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 ...

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

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 ...

1

My best stab at this would be to attach parallel inputs of: Gas1(100psi) -> Flow Meter1 -> Valve1 -> Manifold Input1 Gas2(100psi) -> Flow Meter2 -> Valve2 -> Manifold Input2 Gas3(100psi) -> Flow Meter3 -> Valve3 -> Manifold Input3 ...where: I picked "100psi" to stress that the input pressure should be >> the output pressure. Could be 50psi, or whatever... ...

1

In, compressible flow, the mass flow rate remains constant throughout the flow. But volume flow rate is changed according to the local velocity and area of cross-section. So one can calculate the volume flow rate locally by diving the mass flow rate by local density. Let say, If you need volume flow rate at the exit, At the exit, the pressure is 1 bar and ...

1

The Bernoulli Equation can be considered to be a statement of the conservation of energy, i.e. the internal energy of the fluid remains constant. This can be useful for certain calculations e.g. the Venturi effect In a long pipe run, however, the internal energy is not constant, as some is lost. Any frictional effects (due to surface roughness of the pipe, ...

1

You are dealing with a multi-input multi-output system (MIMO) system in which case you can't in general apply the same techniques as for single-input single-output (SISO) systems. If you are dealing with a linear time invariant MIMO system, then you could use something called the relative gain array to see how well a SISO control approach would work. However ...

1

Control problems are usually easier if you specify The measured variables, I assume $T_{in}$ and $T_{out}$ The manipulated variables, I assume the pump speed according to your description The objectives of the controller. Do you need to be exactly at 90 degC or would and outlet with a certain offset be acceptable? Or is the temperature very important and ...

1

Try using a diffusor. But to give you an equation which helps your problem, we need more information about your air flow. Most important is: Air temperature, velocity, heat capacity ratio of your gas (for air approximately around 1.4). This helps to calculate the Mach-number. If it is lower than 0.3 you can just use the Bernoulli equation to get your result....

1

Elegant, robust, and low cost don't often occur at the same time ;-) What you are wanting to do is not trivial, especially reliably at high temperature. I would start with an "automatic butterfly damper". Most the available dampers will be for hvac equipment and it will take two to achieve your diversion functionality, but they are relatively low cost. You ...

1

Yes, weight percent of a component is the mass (flow rate) of that component divided by the total mass (total flow rate). Total flow rate is equal to the sum of the flowrates of every component.

1

Fiber optics depend on the surface reflecting light by total internal reflection. Therefore the properties of the outer surface are crucial, and reflection depends on what your understanding of a "stream" is. If the water is in direct contact with anything solid (or liquid) (most likely anything but air), it will not work. Total internal reflection depends ...

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