Ankara to Brussels is about 2,502 km and usually takes around 4h in the air. The track it follows runs over the Anatolian plateau, the Black Sea, the Balkans, the Eastern European plains, Central Europe, and Western Europe.
Air lifting over the Anatolian plateau can raise brief, light ripples at cruise; crews know these spots well and the movement stays gentle. Over the Black Sea, the Balkans, the Eastern European plains, Central Europe, and Western Europe the air is usually calm and settled. This track threads jet-stream latitudes, so in winter you may feel a few minutes of light, choppy air high up; summer usually rides calmer.
For most of a flight this length you are at a steady cruise above the weather, where the ride is smooth; the livelier moments, if any, are short.