Reef Central Online Community - View Single Post - Scale model

dkeller_nc · 10/01/2017, 10:26 AM

There are plenty of places to purchase glycerol that are much cheaper than $1,000 per 130 lbs. The price of glycerol varies greatly depending on the purity. Spectrophotometric grade is very pricey, but food grade glycerol is comparatively cheap. I spent no effort on this, just one search, and came up with this.

A couple of suggestions/comments to reach your goal. While real-world empirical experiments are easy to understand and provide a "hands-on" experience, most engineering firms will at least start with a numerical model. The necessary theoretical underpinnings of finite element analysis models have been around for 50+ years, but the gigantic drop in computational cost in the modern era has made them very practical.

I'm not familiar with Wolfram's system - if it allows a drop-in CAD shape and flow field, that might be a viable solution. But one typically does these sorts of things in ProEngineer. It's a very expensive program, so not really suitable for hobbyist use. However, ProEngineer is almost a de rigueur course in most US university engineering departments, particularly in mechanical engineering departments.

And in many cases, university programs are looking for "real world examples" for their design classes. If you've a local university with a strong engineering college, and can make friends with one of the department professors that teaches either a dedicated ProEngineer class or that teaches a Senior Design class, you might be able to convince them to use your proposed system as a case study. One thing to offer to pique their interest is the scale model - they do the computational model, you build a prototype to test their results and present it to the class.

That might put you under the gun to get the prototype done on a schedule so that the students that do the modeling get the feedback from the scale model testing, but the results might actually be publishable in a magazine like Coral, if that interests you.

By the way, regarding using glycerol for your scale model: in my opinion, it's not worth scaling the viscosity. You can get very good approximations from mathematical transformations of measured velocity fields in a scale model to estimate a full-scale system. This is one reason why hydrology/fluid dynamic laboratories that do nautical engineering use unadulterated water to do testing of scale-model ships. But if you choose to use the glycerol, recognize that glycerol will support bacterial growth. So you will want to add a bacterial growth inhibitor to your solutions if you want to keep it around for a few months to do repeated experimentation.

10/01/2017, 10:26 AM	#45
dkeller_nc Registered Member Join Date: Mar 2013 Location: Central NC Posts: 5,062	There are plenty of places to purchase glycerol that are much cheaper than $1,000 per 130 lbs. The price of glycerol varies greatly depending on the purity. Spectrophotometric grade is very pricey, but food grade glycerol is comparatively cheap. I spent no effort on this, just one search, and came up with this. A couple of suggestions/comments to reach your goal. While real-world empirical experiments are easy to understand and provide a "hands-on" experience, most engineering firms will at least start with a numerical model. The necessary theoretical underpinnings of finite element analysis models have been around for 50+ years, but the gigantic drop in computational cost in the modern era has made them very practical. I'm not familiar with Wolfram's system - if it allows a drop-in CAD shape and flow field, that might be a viable solution. But one typically does these sorts of things in ProEngineer. It's a very expensive program, so not really suitable for hobbyist use. However, ProEngineer is almost a de rigueur course in most US university engineering departments, particularly in mechanical engineering departments. And in many cases, university programs are looking for "real world examples" for their design classes. If you've a local university with a strong engineering college, and can make friends with one of the department professors that teaches either a dedicated ProEngineer class or that teaches a Senior Design class, you might be able to convince them to use your proposed system as a case study. One thing to offer to pique their interest is the scale model - they do the computational model, you build a prototype to test their results and present it to the class. That might put you under the gun to get the prototype done on a schedule so that the students that do the modeling get the feedback from the scale model testing, but the results might actually be publishable in a magazine like Coral, if that interests you. By the way, regarding using glycerol for your scale model: in my opinion, it's not worth scaling the viscosity. You can get very good approximations from mathematical transformations of measured velocity fields in a scale model to estimate a full-scale system. This is one reason why hydrology/fluid dynamic laboratories that do nautical engineering use unadulterated water to do testing of scale-model ships. But if you choose to use the glycerol, recognize that glycerol will support bacterial growth. So you will want to add a bacterial growth inhibitor to your solutions if you want to keep it around for a few months to do repeated experimentation.