module Numeric.HFoil.Naca4( Naca4(..)
, coords
, yt
, dyt
, naca4
) where
naca4 :: (Read a, Fractional a) => String -> Naca4 a
naca4 name@(m_:p_:t0:t1:[]) = Naca4 m p t ("NACA "++name)
where
m = 0.01 * read [m_]
p = 0.1 * read [p_]
t = 0.01 * read (t0:[t1])
naca4 _ = error "not a 4 digit airfoil"
data Naca4 a = Naca4 { naca4_m :: a
, naca4_p :: a
, naca4_t :: a
, naca4_name :: String
} deriving Show
yc :: (Ord a, Fractional a) => Naca4 a -> a -> a
yc (Naca4 {naca4_p = p, naca4_m = m}) xc
| xc < 0 = error "xc < 0"
| xc <= p = m/(p*p)*(2*p*xc xc*xc)
| xc <= 1 = m/((1p)*(1p))*((12*p) + 2*p*xc xc*xc)
| otherwise = error "xc > 1"
dyc :: (Ord a, Fractional a) => Naca4 a -> a -> a
dyc (Naca4 {naca4_p = p, naca4_m = m}) xc
| xc < 0 = error "xc < 0"
| xc <= p = m/(p*p)*(2*p 2*xc)
| xc <= 1 = m/((1p)*(1p))*(2*p 2*xc)
| otherwise = error "xc > 1"
yt :: (Ord a, Floating a) => Naca4 a -> a -> a
yt (Naca4 {naca4_t = t}) xc
| xc < 0 = error "xc < 0"
| xc > 1 = error $ "xc > 1"
| otherwise = 5*t*(0.2969*sqrt(xc) 0.1260*(xc) 0.3537*(xc)**2 + 0.2843*(xc)**3 0.1015*(xc)**4)
dyt :: (Ord a, Floating a) => Naca4 a -> a -> a
dyt (Naca4 {naca4_t = t}) xc
| xc < 0 = error "xc < 0"
| xc > 1 = error "xc > 1"
| otherwise = 5*t*(0.5*0.2969/sqrt(xc) 0.1260 2*0.3537*(xc) + 3*0.2843*(xc)**2 4*0.1015*(xc)**3)
coords :: (Ord a, Floating a) => Naca4 a -> a -> ((a,a),(a,a))
coords foil xc
| naca4_m foil == 0 = ((xc,yt_), (xc,yt_))
| otherwise = ((xu,yu ), (xl, yl ))
where
yt_ = yt foil xc
yc_ = yc foil xc
yu = yc_ + yt_ * (cos theta)
yl = yc_ yt_ * (cos theta)
xu = xc yt_ * (sin theta)
xl = xc + yt_ * (sin theta)
theta = atan $ dyc foil xc