Total Drag Chapter 2 Lecture 7 Total Drag

Total Drag Chapter 2 Lecture 7

Total Drag • Total drag is made up of the sum of parasite drag and the induced drag. • Figure 3 -15 p. 74 – The parasite drag starts off at zero velocity and increases – The induced drag at zero velocity and drops off inversely – The point where tow curves cross is drag minimum.

Drag Minimum • Above and below this point drag increases. • Range, rate of climb, and fuel consumption can be improved by slowing down the airplane to a certain point. • Below that point performance begins to deteriorate again due to induced drag is building up more rapidly than parasite drag is reducing.

Equivalent Flat Plate Area • This method of measuring drag, the parasite drag of the airplane is represented by the drag of a flat plate in the airstream. • The equivalent flat plate area is really the ratio of parasite drag to dynamic pressure.

Parasite Drag Coefficient • The ratio of parasite drag to dynamic pressure times the area (wing area) • The flat plate area and the parasite drag are related through the wing area. • Table 3 -1 p. 75 – What do we notice?

Pros of using flat plate area to calculate drag • Convenient way to sum the drag of various components. • Good comparison of the relative aerodynamics efficiency of various designs • Flat plate area can be used to add up drag of various components of the airplane.

Special Types of Parasite Drag • Interference Drag – arises due to the junction of two bodies (wing & fuselage) • Cooling Drag – associated with engine cooling (cowl flaps) • Profile Drag – wing’s parasite drag (drag in profile shape related to angle of attack)

Summary of Drag Definitions • • DEFINE EACH: Pressure drag (form drag) Skin friction drag (viscous drag) Profile drag Interference drag cooling drag induced drag

Ground Effect • Drag alteration when flying near the ground • A cushion of compressed air • Downwash caused by vortex formation at wing tip • When are you in ground effect?

Quiz on Lecture 7 Chapter 2 Please take out a sheet of paper Include today’s date and your name

Quiz on Lecture 7 Chapter 2 • List and explain 3 types of drag discussed today. • What is ground effect?