ENH: support frequency or period for Sine/Square Function1 (#1917)

- For slow oscillations it can be more intuitive to specify the
  period.

ENH: separate mark/space for Square

- makes it easier to tailor the desired intervals.

BUG: incorrect square wave fraction with negative phase shifts

ENH: additional cosine Function1

STYLE: avoid code duplication by inheriting Cosine/Square from Sine.

src/OpenFOAM/primitives/functions/Function1/Cosine/Cosine.H

@@ -0,0 +1,170 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2020 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    Foam::Function1Types::Cosine
+
+Description
+    A templated cosine function, with support for offset etc.
+
+    The wave period can be specified directly
+
+        \f[
+            a cos(2 \pi (t - t0) / p)) s + l
+        \f]
+
+    Or it can be specified by the frequency
+
+        \f[
+            a cos(2 \pi f (t - t0)) s + l
+        \f]
+
+    where
+    \vartable
+        Symbol  | Description       | Units
+        a       | Amplitude         | -
+        f       | Frequency         | [1/s]
+        p       | Period            | [s]
+        s       | Type scale factor | -
+        l       | Type offset level | -
+        t       | Time              | [s]
+        t0      | Start time offset | [s]
+    \endvartable
+
+    The dictionary specification would typically resemble this:
+    \verbatim
+    entry1
+    {
+        type        cosine;
+        frequency   10;
+        amplitude   0.1;
+
+        // A scalar Function1
+        scale       2e-6;
+        level       2e-6;
+    }
+    entry2
+    {
+        type        cosine;
+        frequency   10;
+
+        // A vector Function1
+        scale       (1 0.1 0);
+        level       (10 1 0);
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+        Property  | Description             | Type | Reqd | Default
+        type      | Function type: cosine   | word | yes |
+        amplitude | Amplitude               | Function1<scalar> | no | 1
+        frequency | Frequency [1/s]         | Function1<scalar> | or period |
+        period    | Period [s]              | Function1<scalar> | or frequency |
+        scale     | Scale factor (Type)     | Function1<Type> | yes |
+        level     | Offset level (Type)     | Function1<Type> | yes |
+        t0        | Start time offset       | scalar       | no | 0
+    \endtable
+
+Note
+    For slow oscillations it can be more intuitive to specify the period.
+
+SourceFiles
+    Cosine.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef function1Types_Cosine_H
+#define function1Types_Cosine_H
+
+#include "Sine.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace Function1Types
+{
+
+/*---------------------------------------------------------------------------*\
+                            Class Cosine Declaration
+\*---------------------------------------------------------------------------*/
+
+template<class Type>
+class Cosine
+:
+    public Function1Types::Sine<Type>
+{
+public:
+
+    // Runtime type information
+    TypeName("cosine");
+
+
+    // Generated Methods
+
+        //- No copy assignment
+        void operator=(const Cosine<Type>&) = delete;
+
+
+    // Constructors
+
+        //- Construct from entry name and dictionary
+        Cosine(const word& entryName, const dictionary& dict)
+        :
+            Sine<Type>(entryName, dict)
+        {}
+
+        //- Copy construct
+        explicit Cosine(const Cosine<Type>& rhs)
+        :
+            Sine<Type>(rhs)
+        {}
+
+
+    //- Destructor
+    virtual ~Cosine() = default;
+
+
+    // Member Functions
+
+        //- Return value for time t
+        virtual inline Type value(const scalar t) const
+        {
+            return Sine<Type>::cosValue(t);
+        }
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Function1Types
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //