Examining Bernoulli’s Principle

through the McKee Breezeway

Measuring the Effects of Building Construction on Wind FlowThrough a Structure

Ross Kononen, Keri Bowling, Nick Horianopoulos, and Matt Nolen

Scientific Observation• McKee Hall’s breezeway

– Uncomfortable!– Cold– Windy

Scientific Observation- Ross Kononen noticed wind while

skateboarding

Scientific Question

• Why does the wind velocity appear to increase inside of the McKee breezeway?

• Probable Cause: Dynamic of wind changed by some property of building

Hypothesis• If the McKee Hall Breezeway acts as

a venturi, then: 1. High pressure will exist in

front of and behind the breezeway

2. Low pressure will exist within the breezeway

3. The velocity within the breezeway will increase due to the pressure differential between the outside and the inside of the breezeway

Supporting Literature• Blocken B, Stathopoulos T, Carmeliet J. (2008) Wind environmental

conditions in passages between two long narrow perpendicular buildings. Journal of Aerospace Engineering – ASCE 21(4): 280-287

• Gaimbattista, A., Richardson, B., & Richardson, R.C. (2010) Physics (2nd ed.). New York, NY: McGraw-Hill Companies, Inc.

• Heim, D., and Klemm, K., (2009) LOCAL WIND AND RAIN CONDITIONS IN SEMI-CLOSED NARROW CORRIDORS BETWEEN BUILDINGS , Eleventh International IBPSA Conference, Glasgow, Scotland July 27-30, 2009 1745 – 1752.

• McIlveen, J. F. R., (2002) The everyday effects of wind drag on people, Weather , Vol. 57, pp. 410-417

• Serway, R.A., Faughn, J.S. Vuille, C., Bennett, C.A., (2006) College Physics, (7th ed.), Belmont, CA: Thomas Brooks/Cole, Ch. 6, 160-164

• APB Foundation. (1998). Session 9, Part B: Surface Area and Volume. Retrieved November 04, 2011, from Learning Math: Measurement: http://www.learner.org/courses/learningmath/measurement/session9/solutions_b.html#b8

Examination of Space

}

Examination of SpaceInitial Speed 2.995 m/sFinal Velocity 0. 939 m/s

Outside headwind 2.995 m/sInside headwind???

8.3mIgnored:

• Friction (ground, wheels, Ross’ hair)

• Rotational losses• Vectors

from motion equations

4.25s

an estimate

We thought we could model a value for the wind slowing Ross down

Estimation of Wind Speed

if mVmVptF Used momentum equation to determine force required to slow Ross down:

t

pFav

s

mKg

7.238

s

m 939.0 kg 116.1

s

m 2.995 kg 116.1

Nssm

Kg2.56

25.4

7.238

Estimation of Wind Speed

N)(in force drag 2

2

AvCd

Estimation of Drag Force (modeled at 0.50)

Where:

Air Density, usually 1.2 kg/m3

dC Coefficient of Drag, 0.5 (McIlveen 2002)

A Area, m2

v Velocity in m/s56.2N 4247.050.0

2

2.122

3

vmmKg

s

m01.18

s

m 2.995 of headwind original

s

m21.0v

known from momentum equation

Estimation of Wind Speed

Estimation of Drag Force (modeled at 0.85)

Where:

Air Density, usually 1.2 kg/m3

dC Coefficient of Drag, 0.85 (Engineering Toolbox, 2011)

A Area, m2

v Velocity in m/s56.2N 4247.085.0

2

2.122

3

vmmKg

s

m11.13

s

m 2.995 of headwind original

s

m.161v

known from momentum equation

N)(in force drag 2

2

AvCd

Rosstimation• Ross is 6’4” or 193 cm• Make a square with arms out• Fingertip-fingertip distance is

roughly your height• Square that value, 3/5ths = surface

area (Annenberg Foundation 2011)•Only 19% surface area

exposed to relative wind•Side profile 4247cm2 or 0.4247m2

{19%

Physicist Approved!

• Dr. Matthew Semak• Numbers and physics “make sense”

So to review…

• 13-18 m/s (46 kph to 65 kph) gusts slowing a skateboarder in 8m and 4 ¼ seconds inside McKee Breezeway

• We should expect values somewhat close to these if hypothesis = valid (a 1:~7 down to a 1:4 ratio of speed inside to speed outside)

• We began our research!

Data Collection

• We collected data…

Data Collection

• Three data collectors• Data taken:

– 10 readings– 30 seconds– 5 minutes total

Data Collection

Equidistant, along centerline

Data Collection• We used calibrated anemometers• Precision to the 1/10th m/s

Collection Problem

• Notes– Surprisingly few windy days

• 10 attempts, 3 conditions of observable data

Collection Problem• Unique weather conditions

– When in Colorado is it not windy during Fall?

– Four years history – winds low in 2011!

• Wind mostly came from out of NNE– Also unusual

• Last reading came out of SSW!– Low wind readings outboard– High wind readings inside– Supporting?

Collection Problem

October 2011

October 2010

Findings

1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

12

14

Observations on Oct. 20, 2011

Trial Number

Win

d V

elo

city

(km

/h)

1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

12Observations on Oct. 25, 2011

SE Side of McKee

Breezeway Center

NW Side of McKee

Trial Number

Win

d V

elo

city

(km

/h)

1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

6

7

8Observations on Nov. 6, 2011

Trial Number

Win

d V

elo

city

(km

/h)

Findings

Mostly shows higher wind values outside of breezeway

than inside!

AHHHHHH!

SE side Breezeway NW side0

1

2

3

4

5

6

7

8

9

Average Wind Velocities from Measurement Points

Oct. 20

Poly-nomial (Oct. 20)

Oct. 25

Measurement Point

Ave

rag

e W

ind

Vel

oci

ty (

km/h

)

FindingsDo we reject hypothesis?

•Majority of observations do not support hypothesis•Curious conditions cause suspicion•Not enough data able to be taken to support conclusion either way

•Why??

Analysis•What we think happened:

High pressure(low speed)

Low

pre

ssur

e

(hig

h sp

eed)

1

Low

pre

ssur

e

(hig

h sp

eed)

1

Potential Sources of Error

• Trees• Measurement error

– Face into wind?

• Oddball weather conditions

October 2011

October 2010

Applying this to classroom•Teach learners that science is

complex•Object lesson: wind patterns, historical data•You may have to make many observations to prove or disprove hypothesis•Inquiry based projects promote group work skills•You may not just get different results, you may get results that don’t match observations•Knowledge of Bernoulli’s Principle can help students make better decisions during the course of their lives