Photo Adventures with Curiosity and Learning

April 1, 2010:From SIN to EWR with Yen Ping and Kok Mun

    Learning Links Exploring Vortex generation and vapor condensation: (Nacelle Strakes = Vortex Control Devices, VCD)
  • Vortex generators (Wikipedia)
  • Wing Vortex Generators
  • Nacelle vortex generation
  • How vortex generators work
  • Flow Separation (Wikipedia)
  • Numerical Research of the Nacelle Strake on a Civil Jet
  • Overview of vortext effects on wing lift
  • DC10 Nacelle Strake
  • Computational fluid dynamics(Wikipedia)
  • Boeing 737 Look at thee 737-400. A single inboard strake on each nacelle
  • Airbus A318 Note both inboard and outboard strakes on each nacelle - apparently the placement of strakes is limited for Boeing
  • Note only inboard strakes on the Boeing 777
  • From Dick Shevell AIAA paper : Aerodynamic Bugs: Can CFD Spray Them Away? AIAA Paper 83-2063, August 1983
    DC-10 wind tunnel tests showed a significant loss in maximum lift coefficient in the flap deflected configurations, with landing slat extension, compared to predictions. This resulted in a stall speed increase of about 5 knots in the approach configuration. The initial wing stall occured behind the nacelles and forward of the inboard ailerons. The problem was traced by flow visualization techniques to the effects of the nacelle wake at high angles of attack and the absence of the slat in the vicinity of the nacelle pylons. The solution was developed in the NASA Ames Research Center 12 ft. pressurized tunnel and turned out to be a pair of strakes mounted forward on each side of the nacelles in planes about 45 degrees above the horizontal. The final strake shape was optimized in flight tests. The strakes are simply large vortex generators. The vortices mix the nacelle boundary layer air with the free stream and reduce the momentum loss in the wake. The vortices then pass just over the upper surface of the wing, continuing this mixing process. The counterrotating vortices also create a downwash over the wing region unprotected by the slat, further reducing the premature stall. The effect of the strakes is to reduce the required takeoff and landing field lengths by about 6%, a very large effect.

An example of condensation vortex generated by the nacelle strake (from behind the wing)

This was one of the best flights I have had on SQ22 / SQ21. Yen Ping, Kok Mun and MJ and the rest of their cabin crew not only provided wonderful service but these 3 sort of out anticipated me and made this trip one of the best ever. I got some interesting photos of the condensation vortex that is promoted by the nacelle strake (more later) on the engine housing.

Our SQ 22 Flight Path

Looking from Terminal 3 Gate B7

apr 01 1210 from T3 B7

SQ 22 taxi

apr 01 1217 sq22 taxi


apr 01 1220 sq22 taxi


apr 01 1221 sq22 taxi

A flock of birds were flying over the water drain

apr 01 1223 changi birds close

Changi birds close

apr 01 1223 changi birds


apr 01 1225 sq22 taxi


apr 01 1228 sq22 taxi

Runway turn - waiting for incoming flights to land

apr 01 1230 sq22 runway turn

Incoming flight

apr 01 1235 sq22 waiting

For a couple of years, I have been fascinated by the appearance, structure and disappearance of what I call condensation vortices. They appear along the engine housing and off the tip of the wing stabilizers. One of the flight crew referred to the housing plate as a Nacelle Strake. Here is initial vortex formation - you can see the initiation of the vortex at the Nacelle Strake

apr 01 1240 condensation vortex

Closer view of the initiation at the Nacelle Strake

apr 01 1240 vortex dissipation close

Mark Stock apparently (according to Nafees) is a computational fluid dynamics colleague and made this video of vortex behavior. One of the delights of Facebook is making connections such as Mark - which help me to better understand condensation vortices associated with nacelle strakes on A340 and 777 aircraft.

Altitude: 17m

apr 01 1241 vortex turbulance

Altitude: 33m Condensation vortices from engine housing and wing stabilizer

apr 01 1243 dual vortices

Altitude: 43m No condensation vortices

apr 01 1245 nacelle strake no vortex

Altitude: 59m Condensation vortices appear again


apr 01 1249 sq22 vortex init close

Altitude: 74m Continuation

apr 01 1256 sq22 vortex flow

Altitude: >74 m

apr 01 1258 condensation vortex

Altitude: >74 m

apr 01 1262 condensation vortex

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C. Frank Starmer