# John McArthur at Vicksburg

Readers of this site will be familiar with Gen. John McArthur, general for the Union during the Civil War.  Recently I visited the battlefield at Vicksburg and gained more insight into his story–and another twist in family history from the Confederate side too.

# If a Boomer Tells You that “No One Had Air Conditioning,” They’re Out to Lunch

I’ve heard many Boomers–especially in the South–tell you that “no one had air conditioning.”  That’s simply not true.  When Chet and Myrtle moved to Palm Beach in 1957, they made sure they stayed cool with this unit, a Worthington RWC-609 5 ton water-cooled unit.

Chet and Myrtle also faced some of the other problems endemic to Palm Beach.  One of those was climbers, like this cat:

Fortunately the cat wasn’t insufferable like some of the other climbers in Palm Beach!

One problem they didn’t have to deal with was ARCOM, the dreaded Architectural Commission, which holds the power of life or death over real estate, as one poor chap from Switzerland found out.  Below is the bedroom addition under construction.  Now that it’s more than fifty years old, it probably has historical value!

# The Experimental Determination of the Metastatic Height

In the earlier post on buoyancy and stability, methods for the determination of the metastatic height are discussed.  This is yet another method of doing this, taken (with a few modifications) from E.H. Lewitt, Hydraulics and Fluid Mechanics (Sir Isaac Pitman and Sons, 1923.)   This text also has a treatment on the “moment of inertia” method of computing metastatic height.

The metastatic height of a ship or pontoon may be found experimentally whilst the
vessel is floating, if the position of the centre of gravity is known.

Let W be the weight of the ship, which is known, and let G be the centre of gravity. Let a known movable weight m be placed on one side of the ship.  A pendulum consisting of a weight suspended by a long cord is placed in the ship, and the position of the bob when at rest is marked. Let l be the length of the pendulum. The weight m is then moved across the deck through the distance x, the new position of m being denoted by m’. This will cause the ship to swing through a small angle $\theta$ about its metacentre M. Then, as the pendulum inside the ship still remains vertical, the angle $\theta$ may be measured by the apparent deflection of the pendulum.

Let the apparent horizontal displacement of the pendulum weight = y. Then,

$\tan \theta = \frac{y}{l}$

Referring to Fig. 21, the moment caused by W about M equals the moment about M caused by moving m to m’.  Or,

$W \times GM \tan \theta = mx$

from which

$GM = \frac{mx}{W \tan\theta}$

and, as all the quantities on the right of this equation are known, the metacentric height can be calculated.

This experiment is often carried out on a ship in order to determine the exact position of G which is difficult to estimate from the distribution of the ship’s weight.

# Compressible Flow Through Nozzles, and the Vulcan 06 Valve

Most of our fluid mechanics offerings are on our companion site, Chet Aero Marine.  This topic, and the way we plan to treat it, is so intertwined with the history of Vulcan’s product line that we’re posting it here.  Hopefully it will be useful in understanding both.  It’s a offshoot of Vulcan’s valve loss study in the late 1970’s and early 1980’s, and it led to an important decision in that effort.  I am indebted to Bob Daniel at Georgia Tech for this presentation.

## Basics of Compressible Flow Through Nozzles and Other Orifices

The basics of incompressible flow through nozzles, and the losses that take place, is discussed here in detail.  The first complicating factor when adding compressibility is the density change in the fluid.  For this study we will consider only ideal gases.

Consider a simple orifice configuration such as is shown below.

The mass flow…

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# Installing OpenWatcom Fortran 77

We offer the OpenWatcom Fortran 77 on our Fortran 77 Resources page.  Below is a brief video on how to install it.

The installation is pretty straightforward.  If you have a purely 64-bit version of Windows, it won’t install; it doesn’t go beyond 32-bit.  The installation in Wine for Linux is similar and it runs fine there too.