3B Scientific Laminar Flow Apparatus - Manual (Page 2)

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2. Equipment supplied
2 Acrylic glass basins
1 Mask
20 Sheets of velour paper with cut-outs
1 Mini-flask with dye
Swab for dye
Rubber gloves
3. Technical data
Dimensions: approx. 220x140x240 mm3
Weight: approx. 1 kg
4. Operating principle
Due to the capillary effect and the weight of the
water, it is sucked out of the top container, slowly
and constantly flowing down the velour paper. At the
bottom end of the paper it drops down and is col-
lected in the flat bottom container. In order to be
able to observe and record the streamline curve, the
water flow is marked with colour at regular intervals
near the top edge of the container filled with water.
When the flow is frequently coloured at these points,
the streamline curves are marked by the developing
colour lines. At the cut-outs in the velour paper, the
streamlines change. Due to the colour, the respective
paths of the flowing water are made visible. The
streamlines have their initial shape behind the blo-
cking object. Due to the thin water layer and the
flow resistance of the fibres in the velour paper, the
flow velocity is limited to approx. 2 mm/s. It is there-
fore possible to easily observe how the streamline
images of the laminar flow develop. The equipment
is distinguished by its simple testing method, its easy
handling and a safe testing performance. It has the
special advantage that the developing streamline
images can be made permanent by drying the velour
paper sheets for later use.
5. Operation
• Fill the top part of the large glass container with
water up to a few millimetres below the top
edge.
• Then select the required velour paper sheet.
• Soak it with water by either letting water flow
over the paper or by completely dipping it into a
flat container filled with water.
• Bend back the top part of the velour paper, with
the velour side facing the observer.
• Suspend the folded part of the paper over the
edge of the wall of the acrylic glass vessel such
that it reaches well down into the water.
• Smooth out the front of the velour paper with
your hand to remove possible air bubbles be-
tween the wall and the paper.
• Then put the mask over the velour paper sheet
onto the top container (refer to fig. 1).
Fig. 1
• Insert the swab into the bottle with the colour
solution. Then subsequently apply the colour to
the cut-outs on the mask. If there is not enough
colour, repeat this procedure.
• When using dyes be careful not to splash them
on clothing, for example.
Step by step, the respective streamline image devel-
ops on the velour paper.
• Then remove the mask, take the velour paper
out of the container and dry it, for example, by
hanging it on a horizontal cord.
Note: You may easily cut shapes yourself into the
respective pieces of velour paper. Any shape and
position for the object is possible. The velour paper
should be of a light colour.
6. Sample experiments
6.1. Streamline curve of a linear laminar flow
• Use the velour paper sheet without cut-outs.
The colour lines run vertically at regular intervals
(refer to fig. 2).
Result: In a linear laminar flow, all the streamlines
are parallel to each other. The direction and the
velocity of the flow are constant at any point.
6.2 Streamline curve around objects with various
shapes
• Use sheets of velour paper with cut-outs in the
form of a circle, semi-circle and a rectangle one
after the other.
In front of the object, the flow splits. The streamlines
move around the sides of the object. The intervals
between them reduce. The flow reassembles behind
the object. The individual streamlines run at regular