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[fp024e] Cockpit Openings

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Yosuke Yamamoto edited this page Sep 27, 2019 · 6 revisions

fp024e - Cockpit Openings

Introduction

Formula cars generally have a cockpit opening. However, it is not difficult to imagine that the opening will be an aerodynamic disadvantage.

In this study, CFD calculations are performed on several types of formula-style car cockpit openings to examine their effects.

Models

Model Car Overview

fp024e_cfd_whole-car

Cockpit Opening Models

fp024c_cfd_cockpit-openings

The Original Cockpit Opening

  • for the control data
  • Opening Area at Z610mm : 0.348 [m2]
  • fp024e_cfd_original-cockpit

Helmet on Racing Position

  • Opening Area at Z610mm : 0.324 [m2]
  • fp024e_cfd_helmet-on-racing-position

Cockpit Center Bridge

  • Opening Area at Z610mm : 0.313 [m2]
  • fp024e_cfd_center-bridge

Cockpit Center Bridge with Helmet

  • Opening Area at Z610mm : 0.289 [m2]
  • fp024e_cfd_center-bridge-with-helmet

25mm Thicker Headrest

  • Opening Area at Z610mm : 0.262 [m2]
  • fp024e_cfd_25mm-thicker-headrest

Passenger Seat Fairing

  • Opening Area at Z610mm : 0.000 [m2]

  • fp024e_cfd_passenger-seat-fairing

  • However, because the CFD calculation model is mirrored at the center plane for reducing nodes, it is equivalent to the model with the driver and passenger seats both covered with fairings.

    • fp024e_cfd_passenger-seat-fairing_calculation-model

Simulations

SimScale Project URL: https://www.simscale.com/workbench/?pid=4976467516240040687&mi=spec%3A556bf652-d7dd-4ccb-9f29-daede015a919%2Cservice%3ASIMULATION%2Cstrategy%3A98

Conditions

Conditions Freestream Velocity Magnitude Value : 30 [m/s] Ride Height : Front / Rear = 110 [mm] / 110 [mm]

Results - Coefficieints

The Original Cockpit Opening

Coef. Whole Car Body Fr Wheel Rr Wheel
Cm 0.0274 0.0022 0.0211 0.0041
Cd 0.5679 0.4567 0.0490 0.0622
Cl -0.1922 -0.2298 0.0305 0.0071
Clf -0.0687 -0.1127 0.0364 0.0076
Clr -0.1235 -0.1171 -0.0059 -0.0006
CoP 0.6426 0.5095 -0.1925 -0.0791
L/D -0.3384 -0.5031 0.6225 0.1134

Helmet on Racing Position

Coef. Whole Car Body Fr Wheel Rr Wheel
Cm 0.0290 0.0036 0.0213 0.0041
Cd 0.5629 0.4504 0.0493 0.0632
Cl -0.1949 -0.2328 0.0307 0.0072
Clf -0.0684 -0.1128 0.0366 0.0077
Clr -0.1265 -0.1200 -0.0059 -0.0005
CoP 0.6488 0.5155 -0.1920 -0.0740
L/D -0.3463 -0.5169 0.6239 0.1137

Cockpit Center Bridge

Coef. Whole Car Body Fr Wheel Rr Wheel
Cm 0.0319 0.0067 0.0211 0.0041
Cd 0.5638 0.4521 0.0491 0.0626
Cl -0.1948 -0.2322 0.0304 0.0071
Clf -0.0654 -0.1094 0.0363 0.0077
Clr -0.1293 -0.1228 -0.0059 -0.0006
CoP 0.6640 0.5290 -0.1938 -0.0844
L/D -0.3454 -0.5136 0.6181 0.1128

Cockpit Center Bridge with Helmet

Coef. Whole Car Body Fr Wheel Rr Wheel
Cm 0.0320 0.0069 0.0211 0.0040
Cd 0.5618 0.4496 0.0492 0.0630
Cl -0.2008 -0.2385 0.0304 0.0073
Clf -0.0684 -0.1124 0.0363 0.0077
Clr -0.1324 -0.1261 -0.0059 -0.0004
CoP 0.6594 0.5287 -0.1937 -0.0520
L/D -0.3574 -0.5306 0.6186 0.1161

25mm Thicker Headrest

Coef. Whole Car Body Fr Wheel Rr Wheel
Cm 0.0333 0.0082 0.0211 0.0041
Cd 0.5618 0.4498 0.0491 0.0628
Cl -0.1999 -0.2375 0.0304 0.0072
Clf -0.0666 -0.1105 0.0363 0.0077
Clr -0.1333 -0.1269 -0.0059 -0.0004
CoP 0.6667 0.5345 -0.1938 -0.0604
L/D -0.3558 -0.5280 0.6183 0.1152

Passenger Seat Fairing

Coef. Whole Car Body Fr Wheel Rr Wheel
Cm 0.0489 0.0237 0.0216 0.0036
Cd 0.5535 0.4419 0.0492 0.0625
Cl -0.2102 -0.2495 0.0313 0.0080
Clf -0.0562 -0.1010 0.0372 0.0076
Clr -0.1540 -0.1485 -0.0059 0.0003
CoP 0.7328 0.5951 -0.1880 0.0426
L/D -0.3797 -0.5646 0.6373 0.1277

Comparisons

Comparison of Coefficients

Comparison of the Whole Body Coefficients

Coef. Original
Cockpit Opening		 Helmet on
Racing Position		 Center Bridge Center
Bridge & Helmet		 25mm Thicker
Head Rest		 Passenger
Seat Fairing
Cd 0.5679 0.5629 0.5638 0.5618 0.5618 0.5535
Cl -0.1922 -0.1949 -0.1948 -0.2008 -0.1999 -0.2102
Clf -0.0687 -0.0684 -0.0654 -0.0684 -0.0666 -0.0562
Clr -0.1235 -0.1265 -0.1293 -0.1324 -0.1333 -0.1540
CoP 0.6426 0.6488 0.6640 0.6594 0.6667 0.7328
L/D -0.3384 -0.3463 -0.3454 -0.3574 -0.3558 -0.3797

Differences from "Original Cockpit Opening"

Coef. Original
Cockpit Opening		 Helmet on
Racing Position		 Center Bridge Center
Bridge & Helmet		 25mm Thicker
Head Rest		 Passenger
Seat Fairing
∆Cd 0.0000 -0.0050 -0.0041 -0.0061 -0.0062 -0.0144
∆Cl 0.0000 -0.0027 -0.0026 -0.0086 -0.0076 -0.0180
∆Clf 0.0000 0.0003 0.0033 0.0003 0.0021 0.0126
∆Clr 0.0000 -0.0030 -0.0058 -0.0089 -0.0097 -0.0305
∆CoP 0.0000 0.0063 0.0214 0.0168 0.0242 0.0903
∆L/D 0.0000 -0.0078 -0.0070 -0.0189 -0.0173 -0.0413

fp024e_cfd_coef-differences

Cd Comparison

Cockpit Opening Whole Car Body Fr Wheel Rr Wheel
Original Cockpit Opening 0.5679 0.4567 0.0490 0.0622
Helmet 0.5629 0.4504 0.0493 0.0632
Center Bridge 0.5638 0.4521 0.0491 0.0626
Center Bridge & Helmet 0.5618 0.4496 0.0492 0.0630
25mm Thicker Head Rest 0.5618 0.4498 0.0491 0.0628
Passenger Seat Fairing 0.5535 0.4419 0.0492 0.0625

Cd Differences from "Original Cockpit Opening"

Cockpit Opening Whole Car Body Fr Wheel Rr Wheel
Original Cockpit Opening 0.0000 0.0000 0.0000 0.0000
Helmet -0.0050 -0.0063 0.0002 0.0010
Center Bridge -0.0041 -0.0046 0.0001 0.0004
Center Bridge & Helmet -0.0061 -0.0071 0.0002 0.0008
25mm Thicker Head Rest -0.0062 -0.0069 0.0001 0.0006
Passenger Seat Fairing -0.0144 -0.0148 0.0002 0.0002

fp024e_cfd_cd-differences

Cl Comparison

Cockpit Opening Whole Car Clf Clr Body Fr Wheel Rr Wheel
Original Cockpit Opening -0.1922 -0.0687 -0.1235 -0.2298 0.0305 0.0071
Helmet -0.1949 -0.0684 -0.1265 -0.2328 0.0307 0.0072
Center Bridge -0.1948 -0.0654 -0.1293 -0.2322 0.0304 0.0071
Center Bridge & Helmet -0.2008 -0.0684 -0.1324 -0.2385 0.0304 0.0073
25mm Thicker Head Rest -0.1999 -0.0666 -0.1333 -0.2375 0.0304 0.0072
Passenger Seat Fairing -0.2102 -0.0562 -0.1540 -0.2495 0.0313 0.0080

Cl Differences from "Original Cockpit Opening"

Cockpit Opening Whole Car Clf Clr Body Fr Wheel Rr Wheel
Original Cockpit Opening 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Helmet -0.0027 0.0003 -0.0030 -0.0031 0.0002 0.0001
Center Bridge -0.0026 0.0033 -0.0058 -0.0024 -0.0001 0.0000
Center Bridge & Helmet -0.0086 0.0003 -0.0089 -0.0088 -0.0001 0.0003
25mm Thicker Head Rest -0.0076 0.0021 -0.0097 -0.0077 -0.0001 0.0002
Passenger Seat Fairing -0.0180 0.0126 -0.0305 -0.0197 0.0008 0.0009

fp024e_cfd_cl-differences

Cockpit Opening Area and Coefficients

Case Half of
Cockpit
Open
Area m2 		Cd Cl Clf Clr CoP L/D
Original Cockpit Opening 0.3479 0.5679 -0.1922 -0.0687 -0.1235 0.6426 -0.3384
Helmet 0.3237 0.5629 -0.1949 -0.0684 -0.1265 0.6488 -0.3463
Center Bridge 0.3129 0.5638 -0.1948 -0.0654 -0.1293 0.664 -0.3454
Center Bridge & Helmet 0.2887 0.5618 -0.2008 -0.0684 -0.1324 0.6594 -0.3574
25mm Thicker Head Rest 0.2620 0.5618 -0.1999 -0.0666 -0.1333 0.6667 -0.3558
Passenger Seat Fairing 0.0000 0.5535 -0.2102 -0.0562 -0.1540 0.7328 -0.3797

fp024e_cfd_graph_open-area-coef

The overall trend seems as below.

  • The smaller opening area
    • Decreasing the drag
    • Decreasing the front down force
    • Increasing the rear downforce

The graphs other than the case of passenger seat fairing are expanded as below.

fp024e_cfd_graph_open-area-coef_2

Pressure Comparison

fp024e_cfd_p-g_cokpit-openings

Each Still Images

fp024e_cfd_p-1_original-cockpit-opening

fp024e_cfd_p-2_helmet-on-racing-position

fp024e_cfd_p-3_cockpit-center-bridge

fp024e_cfd_p-4_cockpit-center-bridge-with-helmet

fp024e_cfd_p-5_25mm-thicker-headrest

fp024e_cfd_p-6_passenger-seat-fairing

The high pressure in front of the windshield at the front of the cockpit opening and in the front of the headrest at the rear of the cockpit seems to increase the front downforce.

U Magnitude and Streamline Comparison

fp024e_cfd_u-st-g_cokpit-openings

Each Still Images

fp024e_cfd_u-st-1_original-cockpit-opening

fp024e_cfd_u-st-2_helmet-on-racing-position

fp024e_cfd_u-st-3_cockpit-center-bridge

fp024e_cfd_u-st-4_cockpit-center-bridge-with-helmet

fp024e_cfd_u-st-5_25mm-thicker-headrest

fp024e_cfd_u-st-6_passenger-seat-fairing

The flow disturbed by the cockpit opening is smaller, the flow around the rear wing is faster and increases the rear downforce.

Summary

  • The smaller opening area
    • Decreasing the drag
    • Decreasing the front downforce
    • Increasing the rear downforce
  • The high pressure in front of the windshield at the front of the cockpit opening and in the front of the headrest at the rear of the cockpit seems to increase the front downforce.
  • The flow disturbed by the cockpit opening is smaller, the flow around the rear wing is faster and increases the rear downforce.
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