Lecture 10 - Train Resistances II

Question 1

Flow/Aerodynamic Resistance and how its composed

Answer 1

Is a flow resistance generated with air as the flow medium. Rae is composed of:
Frontal stagnation resistance
Skin friction resistance
Rear wake resistance

Question 2

Form resistance

Answer 2

Is the sum of the stagnation and wake resistances

Question 3

Aerodynamic Optimization / Reduction of driving resistance

Answer 3

Lateral panels between boggies cd 80%
Closed underfloor of power and center cars 70%
Pantograph cover 67%
Jacob boggies 56%
Additional lateral cover of bogies 46%

Question 4

Skin friction resistance

Answer 4

If the lenght of the body is larger than zero, appear skin friction resistance which results from shear stresses

Question 5

General aerodynamic resistance

Answer 5

Sum of form resistance and skin friction resistance

Question 6

Aerodynamic Resistance of a single vehicle (draw. Figure 10.1)

Answer 6

Roof resistance, rear resistance, underfloor resistance, side resistance, front resistance, through-flow resistance

Question 7

Aerodynamic resistance of a train (draw. Figure 10.2)

Answer 7

Front resistance of the first vehicle, inter-car resistance, rear resistance of the last vehicle, side, roof and through-flow resistance of all vehicles

Question 8

Leap at Tunnel Entrance

Answer 8

When entering a tunnel, there is an increase in pressure combined with a rise and at the same time an increase in the inflow velocity due to the displaced air flowing away to the rear
Leap dependency: front shape, ratio between tunnel cross section and vehicle cross section

Question 9

Pressure Distribution in Long Tunnel

Answer 9

When driving through a tunnel a pressure build-up takes place at the front of the vehicle.
The sides experience a considerable depression.
Behind the vehicle a suction area is originated

Question 10

Influence factors in Tunnel Passage

Answer 10

Tunnel lenght, cross section and roughness of the tunnel surface

Question 11

Tunnel Aerodynamic resistance

Answer 11

Front resistance, rear resistance on last vehicle (air suction), air gap resistance on all vehicles