Documentation for aerodynamic analysis
5 unresolved threads
5 unresolved threads
Documentation for aerodynamic analysis
Description
Refined the documentation for aerodynamic analysis
Merge request reports
Activity
requested review from @meric.taneri
assigned to @lukas.neuerburg and @meric.taneri
added 13 commits
-
03bd6789...62c47a87 - 12 commits from branch
develop - 3ffb6107 - Merge branch 'develop' into 'documentation/aeroanalysis'
-
03bd6789...62c47a87 - 12 commits from branch
mentioned in merge request aircraft-design!105 (closed)
requested review from @philipp.hansmann
assigned to @philipp.hansmann
1 # Getting started {#getting-started} 2 This guide will show you the basic usage of **aerodynamic_analysis**. Following steps are necessary (if you are new to UNICADO check out the [settings and outputs](#settingsandoutputs) first!) 3 4 ## Step-by-step 5 6 It is assumed that you have the `UNICADO Package` installed including the executables. In case you are a developer, you need to build the tool first (see [build instructions on UNICADO website](https://unicado.pages.rwth-aachen.de/unicado.gitlab.io/developer/build/cpp/)). 7 8 1. Take an `aircraft_exchange_file` with a fully designed aircraft (fuselage, wing, empennage and nacelles already sized) 9 2. Fill out the configuration file - change at least: 43 44 ### Lifting Line 45 Lifting Line is a method to calculate the lift distribution and the induced drag. 46 For this purpose, the potential equations are used, i.e. the flow is simplified and assumed to be frictionless, rotationless and incompressible. 47 The wing is reduced to its skeletal lines. 48 This simplified geometry is divided into trapezoidal elementary wings, which are covered with free and bound vortices. 49 A system of equations is constructed from the vortex system and the boundary conditions, the solution of which is used to calculate the lift distribution. 50 For a more in-depth discussion, the dissertation by Horstmann (Horstmann 1987: Ein Mehrfach-Traglinienverfahren und seine Verwendung für Entwurf und Nachrechnung nichtplanarer Flügelanordnungen) is recommended. 51 52 The following picture shows the lifitng surfaces of a typical TAW aircraft discretized into elementary wings according to the lifting line method: 53  54 55 The Prandtl-Glauert transformation is applied to the polars from Lifting Line. 56 Lift coefficients, induced drag and pitch moment coefficients are thus transformed to include the compressibility effects. 57 The lift distribution calculated using lifting line agrees well with CFD results for both the conventional wing and the blended wing body. 58 The calculated induced drag cannot be validated by CFD methods. changed this line in version 3 of the diff
64 The frictional drag/viscous drag/zero lift drag is calculated based on the method of Raymer (Raymer 1992: Aircraft Design: A Conceptual Approach, page 280 ff). 65 Contrary to what the name suggests, the viscous drag also regards influences of the boundary layer, which makes validation by CFD calculations difficult. 66 67 For this purpose, the aircraft is broken down into its individual components, whose drag is calculated from a form factor, interference factor, friction coefficient and the wetted area: 68 69 $ 70 C_{D0} = \frac{\sum(C_{fc}FF_{c}Q_{c}S_{wet,c})}{S_{ref}}+C_{Dmisc}+C_{DLP} 71 $ 72 73 The form factors are calculated using semi-empirical formulas, the interference factors are derived from the recommendations in the text (page 284 f). 74 The friction coefficient is derived from the flow around a flat plate and depends on the Reynolds number and the surface roughness. 75 76 In addition to the drags for the individual components, a 'miscellaneous drag' is calculated. 77 This includes resistance caused by gas entering and leaving the hull through leaks and resistance caused by antennas, protrusions and the like. 78 In total, the viscous drag depends only on the geometry, Reynolds number and Mach number and is thus constant over an entire aircraft polar. 79 But a calibration method is built in which the viscous drag is calibrated using an exponential function based on the lift coefficient. changed this line in version 3 of the diff
1 # Software architecture {#softwarearchitecture} 2 3 The software architecture is structured into various modules and packages, each handling specific task. Below is a description of the main components changed this line in version 3 of the diff
22 |Lift, induced drag and pitching moment with corrections for TAW | Lifting Line | analytical/semi-empirical | Wing and stabilizer for TAW | 23 |Viscous drag | According to Raymer | semi-empirical | Lifting surfaces, fuselages and nacelles | 24 |Wave drag | According to Mason | semi-empirical | Lifting surfaces | 25 |High lift adaptions | According to Raymer and Howe | semi-empirical | TAW configuration | 26 |Trim function | Linear interpolation | - | Trimming via all movable horizontal stabilizer | 27 28 The aim is to extend the method set with new calculation methods of variing fidelites for conventional TAW and and conventional configurations like the BWB. 29 30 ## Strategies 31 32 The methods shown above have certain limitations: 33 - No method can provide all aerodynamic values needed 34 - The methods are only valid for certain flight conditions and aircraft configurations 35 - Most methods need other aerodynamic values as input for their calculation 36 37 Because of these shortcommings, the engineer has to select a suitable set of methods for his aircraft and bundle them together into a **strategy**. changed this line in version 3 of the diff
mentioned in commit c067dadf
Please register or sign in to reply