#IMAGEJ PIV PLUGIN HOW TO#

The higher the number, the more likely the flow is to be turbulent. Without going into too much detail, low values of Re represent a more laminar flow. These characters and the state of flow are related through a parameter scientists call Reynold’s Number (Re). You can change the state of flow from laminar to turbulent by changing a few characterisitcs. The situation above is “ideal flow”, with no turbulence and no resistance of movement where the fluid meets the sphere. Rather than break the streamlines, the streamlines closest to the object will be diverted around the object and then reconvene on the other side.īut this isn’t always the case. Let’s put an object into our volume of flow – a sphere. When running experiments, we normally assume – or create – conditions starting with laminar flow. Merging, breaking, and sometimes even backwards flow, which can create vortices. Turbulent, or unsteady flow, is when streamlines are, well, unsteady or chaotic. The distance between the layers may vary and the layers may have differing velocity, but there is no mixing. Laminar, or steady, fluid is when streamlines occur in layers, with no disruptions. These pathways are known as streamlines, and the concept of these streamlines is what we use to define fluid movement, and to ultimately visualize fluid movement. Now, the fluid is comprised of nothing but particles, which have vectors (direction and speed).Īs the particles move, they follow a path, so it is possible to divide this volume of flowing fluid into tons and tons of paths tracing the movement of each particle. It doesn’t matter how large or small it is, just that there are no walls to worry about. To get at what these means, we need to set up a way to think about fluids (any gas or liquid).

The technical words for these states are ‘laminar’ and ‘turbulent’. There are two main types of flow: steady and unsteady. It all starts with the basic question: how do you know what a fluid is doing around an object? But definitely let me know if I don’t, so I know what I can improve on. This stuff is actually really cool, and I’m going to do my best to present it in a way that will hopefully make sense to everyone, no matter your background. If you’re scared of fluid dynamics (I know I was before I started learning it – people traumatized me with tales of horribly complicated, unsolvable Navier-Stokes equations and I was just like, ‘heh, no thank you’), please keep reading. PIV is an amazing technology, and it has probably revolutionized how we do fluid experiments.īefore I get into the nitty gritty of how it works, though, let’s take a step back and learn some fluid dynamics.

I’ve talked about PIV before in my OceanBots blog, but it definitely deserves its own blog post.

#IMAGEJ PIV PLUGIN HOW TO#

George taught me, Dave, an engineering dude, and my biomechanics lab partner how to set up and analyze Particle Image Velocimetry in experiments. It’s taken a year and a half to begin experiments using PIV, but we’ve finally learned how to use it.

Imagej piv plugin