Airfoil Polar Corrections

stall_limiters(
    aoa,
    cl,
    cd;
    clminid=nothing,
    clmaxid=nothing,
    cl_cutoff_slope=0.1,
    cd_cutoff_slope=0.9,
    N=20,
    blend_hardness=50
)

Cuts off coefficient vs alpha curve at min and max coefficient and places rest of curve from -pi to min coeff and max coeff to pi according to user defined clcutoffslope (default 0.1)

Arguments:

• aoa::AbstractVector{Float} : input angles of attack, in radians
• cl::AbstractVector{Float} : input lift coefficients
• cd::AbstractVector{Float} : input drag coefficients

Keyword Arguments:

• clminid::Float=nothing : manually set index for minimum cl
• clmaxid::Float=nothing : manually set index for maximum cl
• cl_cutoff_slope::Float=0.1 : "post-stall" slope for cl
• cd_cutoff_slope::Float=0.1 : "post-stall" slope for cd
• blend_hardness::Float=50 : hardenss of blend between nominal polar and post-stall modifications.

Returns:

• aoa_ext::AbstractVector{Float} : angles of attack for modified polar, in radians
• cl_ext::AbstractVector{Float} : modified lift coefficients
• cd_ext::AbstractVector{Float} : modified drag coefficients

corrected_clcd(af::AlphaReAF, alpha, Re, Mach, solidity, stagger; kwargs...)

Evaluates and applies on-the-fly corrections for airfoil lift and drag. On-the-fly airfoil polar corrections include solidity/stagger corrections, Prandtl-Glauert compressibility corrections, and transonic lift limits and drag additions.

corrected_clcd!(cl, cd, af::AlphaReAF, Re, alpha, Mach, solidity, stagger; kwargs...)

Evaluates and applies on-the-fly corrections for airfoil lift and drag in place.

corrected_clcd!(cl, cd, Mach, solidity, stagger; kwargs...)

Applies on-the-fly corrections for airfoil lift and drag in place.

corrected_clcd!(cl, cd, af::AlphaAF, alpha, Re, Mach, solidity, stagger; kwargs...)

Evaluates and applies on-the-fly corrections, including Reynolds corrections, for airfoil lift and drag in place

corrected_clcd(cas::InReStSoMaCAS, inflow, Re, Mach, solidity, stagger)

Evaluates cascade lift and drag.

Arguments:

Coefficients

• cl::Float : local lift coefficient
• cd::Float : local drag coefficient

Airfoil Object

• af::AlphaReAF : airfoil object of CCBlade type dependent on angle of attack and Reynolds number

or

• af::AlphaAF : airfoil object of CCBlade type dependent on angle of attack only

or

• cas::InReStSoMaCAS : cascade object depentent on inflow angle, Reynolds number, stagger, solidity, and Mach number.

Flow Angle

• alpha::Float : angle of attack, radians. Used with airfoil types

or

• inflow::Float : inflow angle, radians. Used with cascade types

Flow Conditions

• Re::Float : Reynolds number
• Mach::Float : Mach number

Geometry

• solidity::Float : Local solidity
• stagger::Float : Stagger angle, radians

Keyword Arguments:

• mcrit::Float=0.7 : Critical Mach number

rotorzloc airfoil type parameters for post-stall behavior

• dcl_stall::Float=0.1 : change in cl from incipient to total stall, used in transonic lift limiter correction
• dclda_stall::Float=0.1 : Post-stall lift curve slope

Correction factors that were hard coded in rotorzloc and DFDC

• cdmfactor::Float=10.0 :
• clmfactor::Float=0.25 :
• mexp::Float=3.0 :
• cdmstall::Float=0.1 :
• cdmdd::Float=0.0020 :

Smoothing Paramters

• ssblend_hardness::Float=100.0 : sigmoid blending hardness for solidity/stagger corrections
• transblendhardness::Float=75.0 : sigmoid blending hardness for transonic corrections
• absdx::Float=0.0625 : smooth absolute value Δα (radians) for transonic drag addition

Miscellaneous

• verbose::Bool=false : Boolean of whether to print warnings, etc.

prandtl_glauert!(cl, ma)

In place version of pradtl_glauert.

prandtl_glauert(cl, ma)

Applies Prandtl-Glauert correction

Arguments:

• cl::Float : local lift coefficient

Returns

• cl_corr::AbstractVector{Float} : corrected lift coefficients

prandtl_glauert_factor(mach; verbose=false, blend_range=0.02)

Smoothed Prandtl-Glauert Mach correction factor

Arguments:

• mach::Float : Mach number

Keyword Arguments:

• blend_range::Float=0.02 : range for blending factor and max cutoff (allowing Mach >= 1.0 for continuity)

quadspline(xdata, ydata, xpoint)

Sample data in quadratic spline at give point.

re_drag!(cd, re, re_ref; re_exp=0.5)

In-place version of re_drag.

re_drag(cd, re, re_ref; re_exp=0.5)

Arguments:

• cd::AbstractVector{Float} : input drag coefficients
• re::Float : Current Reynolds number
• re_ref::Float : Reference Reynolds number (at which the cd's were generated)

Keyword Arguments:

• re_exp::Float=0.5 : should be 0.2 for laminar and 0.5 for turbulent flow

Returns:

• cd_corr::AbstractVector{Float} : Reynolds corrected drag coefficients

solidity_and_stagger!(cl, solidity, stagger; blend_hardness=100)

In-place version of solidity_and_stagger.

solidity_and_stagger(cl, solidity, stagger; blend_hardness=100)

Apply smoothed Wallis' cascade correction (see solidity_and_stagger_factor_smooth) to local lift.

Arguments:

• cl::AbstractVector{Float} : input lift coefficients
• solidity::Float : local solidity
• stagger::Float : local stagger (in radians)

Keyword Arguments:

• blend_hardness::Float=100 : hardness of smoothing blends

Returns:

• cl_corr::AbstractVector{Float} : corrected lift coefficients.

solidity_and_stagger_factor(solidity, stagger; blend_hardness=100)

Correction for airfoil data used in a high-solidity cascade application. Correction is used in DFDC airfoils nominally and come from quadratic fits to curves in fig 6-29 "Axial Flow Fans and Ducts" by Wallis (1983). Note that the corrections are really only meant for Wallis' custom airfoil design and specific conditions mentioned in the book.

Arguments:

• solidity::Float : local solidity
• stagger::Float : local stagger (in radians)

Keyword Arguments:

• blend_hardness::Float=100 : hardness for smoothing blends

solidity_and_stagger_factor_smooth(solidity, stagger; blend_hardness=100)

A smoothed version of solidity_and_stagger_factor.

Arguments:

• solidity::Float : local solidity
• stagger::Float : local stagger (in radians)

Keyword Arguments:

• blend_hardness::Float=100 : hardness for smoothing blends

stall_limiters(
    aoa,
    cl,
    cd;
    clminid=nothing,
    clmaxid=nothing,
    cl_cutoff_slope=0.1,
    cd_cutoff_slope=0.9,
    N=20,
    blend_hardness=50
)

Cuts off coefficient vs alpha curve at min and max coefficient and places rest of curve from -pi to min coeff and max coeff to pi according to user defined clcutoffslope (default 0.1)

Arguments:

• aoa::AbstractVector{Float} : input angles of attack, in radians
• cl::AbstractVector{Float} : input lift coefficients
• cd::AbstractVector{Float} : input drag coefficients

Keyword Arguments:

• clminid::Float=nothing : manually set index for minimum cl
• clmaxid::Float=nothing : manually set index for maximum cl
• cl_cutoff_slope::Float=0.1 : "post-stall" slope for cl
• cd_cutoff_slope::Float=0.1 : "post-stall" slope for cd
• blend_hardness::Float=50 : hardenss of blend between nominal polar and post-stall modifications.

Returns:

• aoa_ext::AbstractVector{Float} : angles of attack for modified polar, in radians
• cl_ext::AbstractVector{Float} : modified lift coefficients
• cd_ext::AbstractVector{Float} : modified drag coefficients

transonic_drag_addition!(
    cd,
    cl,
    clcdmin,
    mach;
    mcrit=0.7,
    cdmfactor=10.0,
    clmfactor=0.25,
    mexp=3.0,
    cdmdd=0.0020,
    cdmstall=0.1000,
    absdx=0.0625,
    blend_hardness=50,
)

Smoothed, vecotrized, in-place version of transonic_drag_addition.

Different Arguments:

• cd::AbstractVector{Float} : vector of drag coefficients
• cl::AbstractVector{Float} : vector of lift coefficients

Additional Keyword Argument:

• blend_hardness::Float=50 : hardenss of smoothing blends

transonic_drag_addition(
    cd,
    cl,
    clcdmin,
    mach;
    mcrit=0.7,
    cdmfactor=10.0,
    clmfactor=0.25,
    mexp=3.0,
    cdmdd=0.0020,
    cdmstall=0.1000,
    absdx=0.0625,
)

Drag augmentation due to transonic effects as found in XROTOR and DFDC. Note this is nominally applied to DFDC airfoil evaluation.

Arguments:

• cd::Float : input drag coefficient
• cl::Float : input lift coefficient
• clcdmin::Float : lift coefficient at minimum drag coefficient.
• mach::Float : Mach number

Keyword Arguments

• mcrit::Float=0.7 : critical Mach number
• cdmfactor::Float=10.0 : factor hard coded in XROTOR and DFDC
• clmfactor::Float=0.25 : factor hard coded in XROTOR and DFDC
• mexp::Float=3.0 : factor hard coded in XROTOR and DFDC
• cdmstall::Float=0.1000 : factor hard coded in XROTOR and DFDC
• absdx::Float=0.0625 : smoothing factor for smooth absolute value function

Returns:

• cl_corr:Float : corrected lift coefficient

transonic_lift_limiter(
    cl,
    mach,
    clcdmin,
    clmax,
    clmin,
    dclda;
    mcrit=0.7,
    dcl_stall=0.1,
    dclda_stall=0.1,
    cdmfactor=10.0,
    clmfactor=0.25,
    mexp=3.0,
    cdmstall=0.1000,
)

Airfoil polar corrections due to transonic effects as found in XROTOR and DFDC. Note that this correction is done nominally in the DFDC airfoil evaluation.

Arguments:

• cl::Float : input lift coefficient
• mach::Float : Mach number
• clcdmin::Float : lift coefficient at minimum drag coefficient.
• clmax::Float : maximum lift coefficient
• clmin::Float : minimum lift coefficient
• dclda::Float : lift-curve slope
• mcrit::Float=0.7 : critical Mach number
• dcl_stall::Float=0.1 : cl increment from initial to total stall
• dclda_stall::Float=0.1 : lift curve slope post-stall (1/radians)
• cdmfactor::Float=10.0 : factor hard coded in XROTOR and DFDC
• clmfactor::Float=0.25 : factor hard coded in XROTOR and DFDC
• mexp::Float=3.0 : factor hard coded in XROTOR and DFDC
• cdmstall::Float=0.1000 : factor hard coded in XROTOR and DFDC

Returns:

• cl_corr:Float : corrected lift coefficient

transonic_lift_limiter_smooth!(
    cl,
    mach,
    clcdmin,
    clmax,
    clmin,
    dclda;
    mcrit=0.7,
    dcl_stall=0.1,
    dclda_stall=0.1,
    cdmfactor=10.0,
    clmfactor=0.25,
    mexp=3.0,
    cdmstall=0.1000,
    blend_hardness=50,
)

Smoothed, vectorized, in-place version of transonic_lift_limiter.

Different Arguments:

• cl::AbstractVector{Float} : vector of lift coefficients

Additional Keyword Argument:

• blend_hardness::Float=50 : hardenss of smoothing blends