Tutorial Aerodinamika15 Oktober 2021

M. Fikri Z,

Aerodynamic Analysis

• Obtain CD, CL, and CM and its derivatives

Step-by-step

• Prepare the geometry, airfoil, high lift devices configuration and geometries, aircraft weight and balances.

• List all the components that may affect aircraft aerodynamics characteristics

• List all the configuration including: geometry (deflection, landing gear, etc), performance (speed, altitude, RE, Mach number etc)

• Bagi 2 tim:• Tim 1 mengerjakan CD0 pada AISAT

• Tim 2 mengerjakan DATCOM

List of components

• Torenbeekreference can be the start:

• Main Components (wing, fuselage, htp, vtp, canard)

• Other components (Fairing, landing gear, engine, etc)

• Others (Interference correction, high speed correction, etc)

List of configuration

Example

HLD Landing Gear Speed Altitude ...

Clean Retracted Retracted Vc H_c ...

Takeoff Takeoff configuration (X degrees with c’% chord extended) (Fowler flap)

Extended Vto H_to ...

Etc… ... ... ... ... ...

Methods

• AISAT (based on raymer)

• DATCOM

CD0, dan delta_CD0 AISAT

• Sheet DragBreakDown

Wing

Tail

Strut

Pylon

Fuselage

Canopy

Nacelle (s)

Nose Landing Gear

Main Landing Gear

Flap

Engine Out

Leakage

Fuselage Upsweep

Windshield

Base Drag

CD0, dan delta_CD0 AISAT

• The reference value

HLD

Sref Luas penampang tampak atas dari komponen

t/c, x/c, ref chord Refer to airfoil characteristics

Swet Luas seluruh permukaan suatu komponen

Amax Max cross section area

I (m) Panjang suatu komponen

A frontal Luas penampang tampak depan (nose) dari komponen

q/D Semacam funsi bentuk. Seberapa dekat suatu benda dengan bentuk tertentu.

DATCOM, generic

• DATCOM ver 1.4, Holy Cow version

• The basic information is documented enough in the datcom manual, so please refer to the documents.

• This tutorial is only to point out how to read and analyze the results, which are not clear enough in DATCOM.

DATCOM

• All of the input is clear enough in the datcom manual, so please refer to the documents.

• This tutorial is only to point out which input is needed and how to read the results, which are not clear enough in DATCOM.

DATCOM

• Kapabilitas Datcom

DATCOM, initial

• DIM M or DIM FT, input dimensi apakah SI atau US

• DERIV DEG or DERIV RAD, output turunan dalam satuan derajat atau radian

• DAMP: Apakah output dynamic damping dihitung atau tidak

• BUILD: Output per komponen

DATCOM, the output

• Use BUILT so u can get output from each component

• You can add up all the components to obtain the aircraft aerodynamic characteristics

• Highspeed characteristics is included in DATCOM results

This meant the value is the same for other alpha

DATCOM, initial

• FLTCON: flight conditions. WT dan MACH/RNN (tabel kanan)

• OPTINS: references value, wingarea (SREF), chord reference (CBARR), dan span reference (BLREF). Reference ini akan digunakan untuk menghitung semua konstanta. Jika tidak ada DATCOM akan menghitungkan dari geometri input.

• SYNTHS: reference value terkait posisi cg dan posisi sayap, htp, dan vtp. Akan digunakan untuk perhitungan DATCOM (mostly terkait momen dan faktor koreksi)

DATCOM, initial

• FLTCON:

• OPTINS:

• SYNTHS:

• Max input for array is always 20.

DATCOM, canard and three surface

• You need to run two simulation

• You can add the canard result to the WING-HTP configuration to obtain full aircraft.

WGPLNF, WGSCHR HTPLNF, HTSCHR

1. Wing-HTP Wing HTP

2. Canard-Wing Canard Wing

DATCOM, WGPLNF, HTPLNF, VTPLNF

• Input WGPLNF, HTPLNF dan VTPLNF kurang lebih sama• Maksimum model adalah 2 segmen. Jika yang didesain lebih dari dua

segmen dapat diekuivalensikan ke 2 atau 1 segmen.• Semispan(SSP**), chord(CHRDI**), swept(SAVS*), twist (TWISTA), dihedral

(DHAD*)• CHSTAT adalah titik referensi sudut swept (dan twist). Ada di berapa persen

chord? (Typically angka yang dipakai 0.25 = 25%)

• Incidence ada di SYNTHS

DATCOM, WGSCHR, the AIRFOIL

• There is “two” ways to input non NACA airfoil

1. By using coordinate (DATCOM wilcalculate this method will be converted to airfoil characteristics in 2D method)

2. By using airfoil characteristics: 2D Aerodynamics (Cl, Cd, Cm), and simplified geometries (a little bit tricky to calculate).

MS17 Airfoil Coordinate

ASK 21’s Wing Airfoil Characteristics

DATCOM, WGSCHR, the AIRFOILSometimes the 1st method does not have the correct results

Alpha @ CL=0 may not be the same between airfoil and wing (with incidence correction of course)

This can be corrected by:

1. Manually correcting the result

2. Add or tweak some parameter from 2nd method, according to what is need. The parameter is:

Example: CLI = 0.0, ALPHAI = -4.0$ (It means at alpha = -4 degree, CL = 0)

Other problem can be solved with this, example: CLA to steep, CLMAX WING > CLMAX AIRFOIL, etc.

-0.5

0

0.5

1

1.5

2

2.5

-10 -5 0 5 10 15 20 25

CL

α

Cruise clean

Wing Airfoil

DATCOM, high lift devices

• High Lift Devices is defined using SYMFLAP

• TE HLD dan LE HLD harus disimulasikan terpisah

DATCOM, high lift devices

• Additional CD and CM from high lift devices is simple

• D(CD MIN) = similar to CD0 Flap metode Raymer/AISAT. Add to all alpha.

• D(CDI) = different value for different alpha (Induced)

• D(CM) = add to all alpha.

DATCOM, high lift devices

• For CL vs Alpha, alpha @ CL max usually moved

• There is differences between D(CL) dan D(CL MAX)

• D(A CL MAX) = Alpha_CLMAXCLEAN - Alpha_CLMAXTO= (Delta CL – Delta Clmax)/CL_alpha

FLAP

DELTA D(CL) D(CM) D(CL MAX) D(CD MIN)(CLA)D (CH)A (CH)D

40 0.789 -0.0753 0.784 0.05333 8.50E-02 NDM

15 0.31 -0.0149 0.122 0.00715 8.41E-02 NDM

0

0.5

1

1.5

2

2.5

-2.00 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00

CL

α (°)

CL vs α

Flap 15 (Take-off) Clean Sea Level

D(CL MAX)

D(CL)

D(a CL MAX)

DCD0 AISAT

• DCD0 Aisat tinggal ditambahkan ke hasil datcom, sesuai dengan kebutuhan

CRUISE TO ...

Landing Gear n/a ...

Canopy ...

.... ... ... ...

CD0 Datcom ...

CD0 Corrected DATCOM + AISAT DATCOM + AISAT ...

THE RESULT

DRAG POLAR

• DCD0 Aisat tinggal ditambahkan ke hasil datcom, sesuai dengan kebutuhan

CD0 K1 K2

Cruise

TO

....

CL VS ALPHA and Derivative

• Graph of: Airfoil, Wing Only, Aircraft @ various config

• CL_Alpha, (daerah linenar)

• CL0

• CLmax

CL0 CL_alpha Clmax

Cruise

TO

....

58 pax turboprop, double-slotted airfoil

CM VS ALPHA (OR CM VS CL) and Derivative

• Aircraft @ various configuration

• CM_Alpha, or CM_CL (daerah linear)

• CM0 (0 degree or 0 CL)

CM0 CM_alpha / CM_CL

Cruise

TO

....

58 pax turboprop, double-slotted airfoil

FINAL RESULT

• The result of the three

CD0 K1 K2 CL0 CL_alpha Clmax CM0 CM_alpha / CM_CL

Cruise

TO

....

FINAL RESULT• DCD0

CRUISE TO ...

Landing Gear n/a ...

Canopy ...

.... ... ... ...

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