COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 2019

0 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 2019
5 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201910 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201915 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201916 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201917 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201920 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201925 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 201930 Degrees Angle of Attack

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 2019Wheel Estimate Net Drag(lift + drag)1 pound = 43.848 watts

DRAG = (+)
LIFT = (-)
43.848

25

RIM

RIM

WHEEL

WHEEL

WHEEL

ANGLE OF ATTACK

LIFT

DRAG

LIFT

DRAG

NET FORCE

degrees

watts

watts

watts

watts

watts

0

0

2.6834976

027.6834976

27.6834976

5-43.146432

3.0649752-43.146432

28.0649752-15.0814568

10-85.94208

3.9375504-85.94208

28.9375504-57.0045296

15-91.64232

5.524848-91.64232

30.524848-61.117472

16-48.2328

5.963328-48.2328

30.963328-17.269472

17-35.560728

6.445656-35.560728

31.445656-4.115072

20-29.290464

6.664896-29.290464

31.664896

2.374432

25-0.001600452

9.558864-0.001600452

34.558864

34.55726355

30-0.002587032

12.628224-0.002587032

37.628224

37.62563697

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul Farrell
By Paul Lew
Gravel Rim Design
NG_Gravel26x33_V7
30 September 2019

COMPUTATIONAL FLUID DYNAMICS (CFD) ANALYSISFor Nex-Gen/ Paul FarrellBy Paul Lew
Gravel Rim Design
NG_Gravel26x33_V730 September 2019

SUMMARY
This is the CFD analysis of the rim only. After adding in the spokes and hub, and based on theresults I would expect that this design will meet or beat the DT Swiss rim GRC 1400
performance.
The tyre diameter in the CFD test is 40 mm.
The NG_Gravel26x33_V7 Gravel Rim Design produces maximum Lift at 15 degrees angle ofattack. The rim begins to stall at 15 degrees angle of attack, which is typical for bicycle rims, butproduces significant lift to 17 degrees angle of attack.
Based on the analysis I can estimate that the wheel will produce forward thrust (lift) from 5 - 17degrees. Below 5 degrees and above 17 degrees DRAG will overcome LIFT.
Although the drag numbers for the rim are low, you can add 20 - 25 watts to the rim DRAG data
to estimate the rim drag. The spokes and hub contribute nearly 100% to DRAG, and the rim
contributes nearly 100% to LIFT.
The rounded symmetrical shape contributes to the stability and high-lift characteristic from 10 15 degrees angle of attack. Drag has a smooth and consistent low exponential curvethroughout the test range.