which hair type curls up like a u shape

Hair that curls up in a U shape is often referred to as having a "U-shaped curl pattern" or could be described as having a loose or relaxed curl type. This type of curl typically falls in the wavy or loosely curled category, which can often be seen in hair types 2 (wavy) and 3A (loose curls) on the hair typing classification system.

In hair type 2, the waves can have a more pronounced S or U shape, while in 3A, the curls are typically larger and bouncier but can still exhibit a U shape. Factors such as hair texture, moisture, and styling techniques can also influence the shape and definition of the curls.

If you're looking to enhance or define U-shaped curls, using the right products, such as curl creams or mousses, combined with heat or diffusing techniques, can help achieve that look.