Christian Malte Iversen

Phase 3 / day ##

Phase 2 / day 7

2011-02-10

The airflow strategy of this structure was to lead air from a high level to ground level, done with a tower-like back. In addition it was the intension to have airflow through the entire ground level. Regrettably it’s hard to say whether this was the case or not since the experiment was done slightly incorrectly and the documentation is crude. Nevertheless my ‘eyes on sight’ enables me to state that the strategy wasn’t perfectly fulfilled. The air swirled, as was intended, between the two flat down identical elements. But this swirl didn’t seem to create the flow from the second to the ground level. Furthermore high pressure in the tower prevented air from really getting into it, only leading the flow around.

Next step of the process is to develop this model further so it may accomplish the airflow strategy better including the flow from the opposite direction. Also the structural needs tending to since the model is rather unstable.

Phase 2 / day 6

2011-02-09

Second phase has now begund and on this first day we transfer some of our settings from phase 1 into a windtunnel.

In the first test (001a) a vortex appears behind the northern wall. It interesting to see that the smoke escapes between the two other walls slightly to the right. My guess is that this effect is due to irregularities, making the setup none symmetrical. The whole setup creates a calm area only disturbed by the little smoke coming from between the walls. Out of the picture, farther to the south, vortices repeatedly appeared on both the left and right side, indicating turbulence created by the walls.

The second test (001b) revealed two vortices behind each of the front walls. This was expected since the test with the salt-setup indicated the same. On both front walls it’s clear to see that the smoke gently splits up into two main streams going around. This is an indication of the high pressure zone in front of the walls. The vortices indicate low pressure zones behind them.

Third test (003a) shows how the airflow is directed around the angled wall by the front wall. The high pressure on the front side seems to be powerful enough to prevent air to be directed in between the walls. The airflow cannot be described as completely laminar, though, since a vortex appears behind the wall farthest to the right.

Fourth test (003b) allows for air to stream between the walls creating a vortex behind the two walls to the right.

Phase 1 / day 5

2011-02-07

The four images above illustrate some of the work done on the last day of phase 1 (airflow is from left to right). The southern wall is kept fixed in a series of test, where only one other wall is moved around. This is done to investigate the effect that this second wall has on the vortex created behind the primary wall. Only in the last setting the vortex is significantly disrupted. This is probably to the cause of the air directed to the right by the secondary wall.

Phase 1 / day 4

2011-02-06

Someone had the annual semester party thrown Thursday, the same day as our third day of experimenting. That, needless to say, rendered all work impossible the following day – the same reason for this late post concerning day four. The tests were instead run Saturday with some remaining hangover.

Test no. 9: As similar to appendix 01_02 element 02 this test shows the appearance of a vortex between the first to walls. Between the second and third (farthest to the right) nothing really happens except for a small area to the south. This could indicate that the airflow in fact is directed in between these two walls, the velocity or “power” is just not strong enough to move the heavy salt.

Test no. 10:The air doesn’t seem to be directed past the third wall as I might anticipate. Instead it is cast to the sides of the wall creating a vortex in the northern area.

Test no. 11:In this setting no sand is blow away inside the space defined by the walls. At the end results it is visible though, that the airflow is directed to some extend into this space since a small hole towards it is showing.

Test no. 12:The airflow is powerful in the southern region where a long straight line of salt is blown away. Behind the skewed wall seems to be a low pressure zone contributing to the occurrence of a vortex.

Phase 1 / day 3

2011-02-03

Today’s work bears the impress of the reviewing of yesterday’s method; mainly that we rushed into conclusions concerning the behavior of the airflow and thus the turbulence. As a result, we decide to repeat the first experiment of day 1 only this time being more aware of the parameters affecting the output. The awareness leads us to construct a wind tunnel in an attempt to eliminate potential turbulence from the air source. This creates new settings for the onward experiments making it difficult, if not impossible, to compare with the results of the past.

The wind tunnel may direct the airflow more evenly onto the wall, but also implies new sources of error; the airflow is not divided equally among all the small pipes.

The following images display end results for four experiments of the first type (end results being 2 minutes of wind exposure).

Image 001: Some of the salt has been moved away from the extreme left and right area behind the wall. This indicates some of the same airflow as yesterday, in which we assumed the presence of swirls.

Image 002-3: Two almost identical tests to verify that we get roughly the same result from both. In attempt to magnify the effect of image 001, distance to the air source is reduced 3 cm. We learn, however, that the effect is instead decreased.

Image 004: Distance to the air source reduced another 2 centimeters (total of 5 cm in comparison to image 001). It seems that the assumed swirls are now completely absent. This indicates that the distance to the air source is a powerful parameter in terms of turbulence. We agree to further investigate the turbulence of this one-wall setting tomorrow.

The next series of experiments investigates a multi-wall setting. While keeping the wall used in the first experiments fixed a second wall is placed behind it in different manners. In these series we observe the humidity of the salt could be an issue affecting the result and agree to change salt tomorrow.

The results are displayed in the below images.

Image 005-6: When too great a distance between the walls, the second seems to have no impact on the result.

Image 007-8: We found these two settings particularly interesting since some kind of turbulence appears in the area between the walls (click the images to play the animation).

Image 009-11: Altering the vertical position of the walls creating an overlap seems to reduce the turbulence.

Phase 1 / day 2

2011-02-02

The following entry is evidence of shared experiments and discussions with several of my fellow students.

To assess the four keywords of phase one, we follow this approach:

Step 1: Basic understanding of airflow

  1. The airflow is directed perpendicular towards the middle of the wall
  2. Knowledge of turbulence is obtained
  3. This experiment is repeated noting different results
  4. Assumptions about airflow and turbulence are drawn.

Step 2: Comparable series of experiments

  1. All factors are fixed except the arrangement of the wall
  2. Orientation is altered 90 degrees and the experiment is repeated
  3. The new conditions for turbulence is discussed
  4. No conclusions are drawn

This image illustration shows one subject of discussion concerning turbulence (click the image to play the animation).

Ill. 1: Image series of turbulence

It quickly became evident that the airflow caused turbulence (as opposed to laminar airflow). The resulting swirl moves the grains of salt away from the area immediate behind the wall but also draws more salt in a small pile next to this area. In this particular experiment another circular area appears where salt is blown away, probably to the cause of the swirl.

The assumptions concerning both the swirl and different air pressures are illustrated below.

 

In this next series of images we consider the orientation and arrangement of the wall. In order to be able to compare the results we stride to keep all factors that could influence the result fixed. The factors we consider are:

  • Direction of the airflow and distance from the source
  • Placement of the camera
  • Placement of the “saltbox”
  • The smooth- and levelness of the salt layer

This last parameter is particularly hard to control since every experiment requires a new leveling of the salt. We tried to distribute the salt with our hands and then shake the box with fairly satisfying results.

As mentioned no definite conclusions are drawn to the results of these experiments.

Regrettably, none of these experiments deals with the velocity of the airflow as in relation to the final keyword “Speed”. This is due to the reduced effect of the experiments with less than full power on the air source, and in the eager to display results in the images the velocity was never reduced.

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